🪄 Filter Function: Modify Inputs and Outputs

Welcome to the comprehensive guide on Filter Functions in Open WebUI! Filters are a flexible and powerful plugin system for modifying data before it's sent to the Large Language Model (LLM) (input) or after it’s returned from the LLM (output). Whether you’re transforming inputs for better context or cleaning up outputs for improved readability, Filter Functions let you do it all.

This guide will break down what Filters are, how they work, their structure, and everything you need to know to build powerful and user-friendly filters of your own. Let’s dig in, and don’t worry—I’ll use metaphors, examples, and tips to make everything crystal clear! 🌟

🌊 What Are Filters in Open WebUI?

Imagine Open WebUI as a stream of water flowing through pipes:

User inputs and LLM outputs are the water.
Filters are the water treatment stages that clean, modify, and adapt the water before it reaches the final destination.

Filters sit in the middle of the flow—like checkpoints—where you decide what needs to be adjusted.

Here’s a quick summary of what Filters do:

Modify User Inputs (Inlet Function): Tweak the input data before it reaches the AI model. This is where you enhance clarity, add context, sanitize text, or reformat messages to match specific requirements.
Intercept Model Outputs (Stream Function): Capture and adjust the AI’s responses as they’re generated by the model. This is useful for real-time modifications, like filtering out sensitive information or formatting the output for better readability.
Modify Model Outputs (Outlet Function): Adjust the AI's response after it’s processed, before showing it to the user. This can help refine, log, or adapt the data for a cleaner user experience.

Key Concept: Filters are not standalone models but tools that enhance or transform the data traveling to and from models.

Filters are like translators or editors in the AI workflow: you can intercept and change the conversation without interrupting the flow.

🗺️ Structure of a Filter Function: The Skeleton

Let's start with the simplest representation of a Filter Function. Don't worry if some parts feel technical at first—we’ll break it all down step by step!

🦴 Basic Skeleton of a Filter

from pydantic import BaseModel
from typing import Optional

class Filter:
    # Valves: Configuration options for the filter
    class Valves(BaseModel):
        pass

    def __init__(self):
        # Initialize valves (optional configuration for the Filter)
        self.valves = self.Valves()

    def inlet(self, body: dict) -> dict:
        # This is where you manipulate user inputs.
        print(f"inlet called: {body}")
        return body

    def stream(self, event: dict) -> dict:
        # This is where you modify streamed chunks of model output.
        print(f"stream event: {event}")
        return event

    def outlet(self, body: dict) -> None:
        # This is where you manipulate model outputs.
        print(f"outlet called: {body}")

🆕 🧲 Toggle Filter Example: Adding Interactivity and Icons (New in Open WebUI 0.6.10)

Filters can do more than simply modify text—they can expose UI toggles and display custom icons. For instance, you might want a filter that can be turned on/off with a user interface button, and displays a special icon in Open WebUI’s message input UI.

Here’s how you could create such a toggle filter:

from pydantic import BaseModel, Field
from typing import Optional

class Filter:
    class Valves(BaseModel):
        pass

    def __init__(self):
        self.valves = self.Valves()
        self.toggle = True # IMPORTANT: This creates a switch UI in Open WebUI
        # TIP: Use SVG Data URI!
        self.icon = """data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIGZpbGw9Im5vbmUiIHZpZXdCb3g9IjAgMCAyNCAyNCIgc3Ryb2tlLXdpZHRoPSIxLjUiIHN0cm9rZT0iY3VycmVudENvbG9yIiBjbGFzcz0ic2l6ZS02Ij4KICA8cGF0aCBzdHJva2UtbGluZWNhcD0icm91bmQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiIGQ9Ik0xMiAxOHYtNS4yNW0wIDBhNi4wMSA2LjAxIDAgMCAwIDEuNS0uMTg5bS0xLjUuMTg5YTYuMDEgNi4wMSAwIDAgMS0xLjUtLjE4OW0zLjc1IDcuNDc4YTEyLjA2IDEyLjA2IDAgMCAxLTQuNSAwbTMuNzUgMi4zODNhMTQuNDA2IDE0LjQwNiAwIDAgMS0zIDBNMTQuMjUgMTh2LS4xOTJjMC0uOTgzLjY1OC0xLjgyMyAxLjUwOC0yLjMxNmE3LjUgNy41IDAgMSAwLTcuNTE3IDBjLjg1LjQ5MyAxLjUwOSAxLjMzMyAxLjUwOSAyLjMxNlYxOCIgLz4KPC9zdmc+Cg=="""
        pass

    async def inlet(
        self, body: dict, __event_emitter__, __user__: Optional[dict] = None
    ) -> dict:
        await __event_emitter__(
            {
                "type": "status",
                "data": {
                    "description": "Toggled!",
                    "done": True,
                    "hidden": False,
                },
            }
        )
        return body

🖼️ What’s happening?

toggle = True creates a switch UI in Open WebUI—users can manually enable or disable the filter in real time.
icon (with a Data URI) will show up as a little image next to the filter’s name. You can use any SVG as long as it’s Data URI encoded!
The inlet function uses the __event_emitter__ special argument to broadcast feedback/status to the UI, such as a little toast/notification that reads "Toggled!"

Toggle Filter

You can use these mechanisms to make your filters dynamic, interactive, and visually unique within Open WebUI’s plugin ecosystem.

⚙️ Filter Administration & Configuration

🌐 Global Filters vs. Model-Specific Filters

Open WebUI provides a flexible multi-level filter system that allows you to control which filters are active, how they're enabled, and who can toggle them. Understanding this system is crucial for effective filter management.

Filter Activation States

Filters can exist in one of four states, controlled by two boolean flags in the database:

State	`is_active`	`is_global`	Effect
Globally Enabled	✅ `True`	✅ `True`	Applied to ALL models automatically, cannot be disabled per-model
Globally Disabled	❌ `False`	`True`	Not applied anywhere - even though the filter is globally enabled, the filter itself is disabled
Model-Specific	✅ `True`	❌ `False`	Only applied to models where the admin explicitly enables it
Inactive	❌ `False`	`False`	Not applied anywhere, even if filter is enabled for a model by the admin - the filter itself is turned off

Global Filter Behavior

When a filter is set as Global (is_global=True) and Active (is_active=True), it becomes force-enabled for all models:

It appears in every model's filter list as checked and greyed out
Admins cannot uncheck it in model settings
It runs on every chat completion request, regardless of model

Admin Panel: Making a Filter Global

Location: Admin Panel → Functions → Filter Management

To make a filter global:

Navigate to the Admin Panel
Click on Functions in the sidebar
Find your filter in the list
Click the three-dot menu (⋮) next to the filter
Click the 🌐 Globe icon to toggle is_global
Ensure the filter is also Active (green toggle switch)

API Endpoint:

POST /functions/id/{filter_id}/toggle/global

Visual Indicators:

🟢 Green toggle = is_active=True (filter is active)
🌐 Highlighted globe icon = is_global=True (applies to all models)

🎛️ The Two-Tier Filter System

Open WebUI uses a sophisticated two-tier system for managing filters on a per-model basis. This can be confusing at first, but it's designed to support both always-on filters and user-toggleable filters.

Tier 1: FiltersSelector (Which filters are available?)

Location: Model Settings → Filters → "Filters" Section

This controls which filters are available for a specific model.

Behavior:

Shows all filters (both global and model-specific)
Global filters appear as checked and disabled (can't be unchecked)
Regular filters can be toggled on/off
Saves to: model.meta.filterIds in the database

Example:

{
  "meta": {
    "filterIds": ["filter-uuid-1", "filter-uuid-2"]
  }
}

Tier 2: DefaultFiltersSelector (Which toggleable filters start enabled?)

Location: Model Settings → Filters → "Default Filters" Section

This section only appears when at least one toggleable filter is selected (or is global).

Purpose: Controls which toggleable filters are enabled by default for new chats.

What is a "Toggleable" Filter?

A filter becomes toggleable when its Python code includes:

class Filter:
    def __init__(self):
        self.toggle = True  # This makes it toggleable!

Behavior:

Only shows filters with toggle=True
Only shows filters that are either:
- In filterIds (selected for this model), OR
- Have is_global=true (globally enabled)
Controls whether the filter is ON or OFF by default in the chat UI
Saves to: model.meta.defaultFilterIds

Example:

{
  "meta": {
    "filterIds": ["filter-uuid-1", "filter-uuid-2", "filter-uuid-3"],
    "defaultFilterIds": ["filter-uuid-2"]
  }
}

Interpretation:

All three filters are available for this model
Only filter-uuid-2 starts enabled by default
If filter-uuid-1 and filter-uuid-3 have toggle=True, users can enable them manually in the chat UI

🔄 Toggleable Filters vs. Always-On Filters

Understanding the difference between these two types is key to using the filter system effectively.

Always-On Filters (No `toggle` property)

Characteristics:

Run automatically whenever the filter is active for a model
No user control in the chat interface
Do not appear in the "Default Filters" section
Do not show up in the chat integrations menu (⚙️ icon)

Use Cases:

Content moderation - Filter profanity, hate speech, or inappropriate content
PII scrubbing - Automatically redact emails, phone numbers, SSNs, credit card numbers
Prompt injection detection - Block attempts to manipulate the system prompt
Input/output logging - Track all conversations for audit or analytics
Cost tracking - Estimate and log token usage for billing
Rate limiting - Enforce request limits per user or globally
Language enforcement - Ensure responses are in a specific language
Company policy enforcement - Inject legal disclaimers or compliance notices
Model routing - Redirect requests to different models based on content

Example:

class ContentModerationFilter:
    def __init__(self):
        # No toggle property - this is an always-on filter
        pass
    
    def inlet(self, body: dict) -> dict:
        # Always scrub PII before sending to model
        last_message = body["messages"][-1]["content"]
        body["messages"][-1]["content"] = self.scrub_pii(last_message)
        return body

Toggleable Filters (`toggle=True`)

Characteristics:

Appear as switches in the chat UI (in the integrations menu - ⚙️ icon)
Users can enable/disable them per chat session
Do appear in the "Default Filters" section
defaultFilterIds controls their initial state (ON or OFF)

Use Cases:

Web search integration - User decides when to search the web for context
Citation mode - User controls when to require sources in responses
Verbose/detailed mode - User toggles between concise and detailed responses
Translation filters - User enables translation to/from specific languages
Code formatting - User chooses when to apply syntax highlighting or linting
Thinking/reasoning toggle - Show or hide model's chain-of-thought reasoning
Markdown rendering - Toggle between raw text and formatted output
Anonymization mode - User enables when discussing sensitive topics
Expert mode - Inject domain-specific context (legal, medical, technical)
Creative writing mode - Adjust temperature and style for creative tasks

Example:

class WebSearchFilter:
    def __init__(self):
        self.toggle = True  # User can turn on/off
        self.icon = "data:image/svg+xml;base64,..."  # Shows in UI
    
    async def inlet(self, body: dict, __event_emitter__) -> dict:
        # Only runs when user has enabled this filter
        await __event_emitter__({
            "type": "status",
            "data": {"description": "Searching the web...", "done": False}
        })
        # ... perform web search ...
        return body

Where Toggleable Filters Appear:

Model Settings → Default Filters Section
- Configure which filters start enabled
Chat UI → Integrations Menu (⚙️ icon)
- Users can toggle filters on/off per chat
- Shows custom icons if provided
- Realtime enable/disable

📊 Filter Execution Flow

Here's the complete flow from admin configuration to filter execution:

1. ADMIN PANEL (Filter Creation & Global Settings)

Admin Panel → Functions → Create New Function
Set type="filter"
Toggle is_active (enable/disable filter globally)
Toggle is_global (apply to all models)

2. MODEL CONFIGURATION (Per-Model Filter Selection)

Model Settings → Filters Section
FiltersSelector: Select which filters for this model
DefaultFiltersSelector: Set default enabled state (only for toggleable filters)

3. CHAT UI (User Interaction - Toggleable Filters Only)

Chat → Integrations Menu (⚙️) → Toggle Filters
Users can enable/disable toggleable filters
Always-on filters run automatically (no UI control)

4. REQUEST PROCESSING (Filter Compilation)

Backend: get_sorted_filter_ids()
Fetch global filters (is_global=True, is_active=True)
Add model-specific filters from model.meta.filterIds
Filter by is_active status
For toggleable filters: Check user's enabled state
Sort by priority (from valves)

5. FILTER EXECUTION

Execute inlet() filters (pre-request)
Send modified request to LLM
Execute stream() filters (during streaming)
Execute outlet() filters (post-response)

📡 Filter Behavior with API Requests

When using Open WebUI's API endpoints directly (e.g., via curl or external applications), filters behave differently than when the request comes from the web interface. Understanding these differences is crucial for building effective filters.

Key Behavioral Differences

Function	WebUI Request	Direct API Request
`inlet()`	✅ Always called	✅ Always called
`stream()`	✅ Called during streaming	✅ Called during streaming
`outlet()`	✅ Called after response	❌ NOT called by default
`__event_emitter__`	✅ Shows UI feedback	⚠️ Runs but no UI to display

Outlet Not Called for API Requests

The outlet() function is only triggered for WebUI chat requests, not for direct API calls to /api/chat/completions. This is because outlet() is invoked by the WebUI's /api/chat/completed endpoint after the chat is finished.

If you need outlet() processing for API requests, your API client must call /api/chat/completed after receiving the full response.

Triggering Outlet for API Requests

To invoke outlet() filters for API requests, your client must make a second request to /api/chat/completed after receiving the complete response:

# After receiving the full response from /api/chat/completions, call:
curl -X POST http://localhost:3000/api/chat/completed \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "llama3.1",
    "messages": [
      {"role": "user", "content": "Hello"},
      {"role": "assistant", "content": "Hi there! How can I help you?"}
    ],
    "chat_id": "optional-chat-id",
    "session_id": "optional-session-id"
  }'

tip

Include the full conversation in messages, including the assistant's response. The chat_id and session_id are optional but recommended for proper logging and state tracking.

Detecting API vs WebUI Requests

You can detect whether a request originates from the WebUI or a direct API call by checking the __metadata__ argument:

def inlet(self, body: dict, __metadata__: dict = None) -> dict:
    # Check if request is from WebUI
    interface = __metadata__.get("interface") if __metadata__ else None
    
    if interface == "open-webui":
        print("Request from WebUI")
    else:
        print("Direct API request")
    
    # You can also check for presence of chat context
    chat_id = __metadata__.get("chat_id") if __metadata__ else None
    if not chat_id:
        print("No chat context - likely a direct API call")
    
    return body

Example: Rate Limiting for All Requests

Since inlet() is always called, use it for rate limiting that applies to both WebUI and API requests:

from pydantic import BaseModel, Field
from typing import Optional
import time

class Filter:
    class Valves(BaseModel):
        requests_per_minute: int = Field(default=60, description="Max requests per minute per user")
    
    def __init__(self):
        self.valves = self.Valves()
        self.user_requests = {}  # Track requests per user
    
    def inlet(self, body: dict, __user__: dict = None) -> dict:
        if not __user__:
            return body
        
        user_id = __user__.get("id")
        current_time = time.time()
        
        # Clean old entries and count recent requests
        if user_id not in self.user_requests:
            self.user_requests[user_id] = []
        
        # Keep only requests from the last minute
        self.user_requests[user_id] = [
            t for t in self.user_requests[user_id] 
            if current_time - t < 60
        ]
        
        if len(self.user_requests[user_id]) >= self.valves.requests_per_minute:
            raise Exception(f"Rate limit exceeded: {self.valves.requests_per_minute} requests/minute")
        
        self.user_requests[user_id].append(current_time)
        return body

Example: Logging All API Usage

Track token usage and requests for both WebUI and direct API calls:

from pydantic import BaseModel, Field
from typing import Optional
import logging

class Filter:
    class Valves(BaseModel):
        log_level: str = Field(default="INFO", description="Logging level")
    
    def __init__(self):
        self.valves = self.Valves()
        self.logger = logging.getLogger("api_usage")
    
    def inlet(self, body: dict, __user__: dict = None, __metadata__: dict = None) -> dict:
        user_email = __user__.get("email", "unknown") if __user__ else "anonymous"
        model = body.get("model", "unknown")
        interface = __metadata__.get("interface", "api") if __metadata__ else "api"
        chat_id = __metadata__.get("chat_id") if __metadata__ else None
        
        self.logger.info(
            f"Request: user={user_email}, model={model}, "
            f"interface={interface}, chat_id={chat_id or 'none'}"
        )
        
        return body

Event Emitter Behavior

Filters that use __event_emitter__ will still execute for API requests, but since there's no WebUI to display the events, the status messages won't be visible. The filter logic still runs—only the visual feedback is missing.

⚡ Filter Priority & Execution Order

When multiple filters are active, they execute in a specific order determined by their priority value. Understanding this is crucial when building filter chains where one filter depends on another's changes.

Setting Filter Priority

Priority is configured via the Valves class using a priority field:

class Filter:
    class Valves(BaseModel):
        priority: int = Field(
            default=0,
            description="Filter execution order. Lower values run first."
        )
    
    def __init__(self):
        self.valves = self.Valves()
    
    def inlet(self, body: dict) -> dict:
        # This filter's execution order depends on its priority value
        return body

Priority Ordering Rules

Priority Value	Execution Order
`0` (default)	Runs first
`1`	Runs after priority 0
`2`	Runs after priority 1

Lower Priority = Earlier Execution

Filters are sorted in ascending order by priority. A filter with priority=0 runs before a filter with priority=1, which runs before priority=2, and so forth.

🔗 Data Passing Between Filters

When multiple filters are active, each filter in the chain receives the modified data from the previous filter. The returned value from one filter becomes the input to the next filter in the priority order.

User Input
    ↓
Model Router Filter (priority=0) → changes parts of the body
    ↓
Context Manager Filter (priority=1) → receives modified body ✓
    ↓
Logging Filter (priority=2) → receives body with all previous changes ✓
    ↓
LLM Request (sends final modified body to OpenAI/Ollama API)

Important: Always Return the Body

If your filter modifies the body, you must return it. The returned value is passed to the next filter. If you return None, subsequent filters will fail.

async def inlet(self, body: dict, __event_emitter__) -> dict:
    body["messages"].append({"role": "system", "content": "Hello"})
    return body  # Don't forget this!

🎨 UI Indicators & Visual Feedback

In the Admin Functions Panel

Indicator	Meaning
🟢 Green toggle	Filter is active (`is_active=True`)
⚪ Grey toggle	Filter is inactive (`is_active=False`)
🌐 Highlighted globe	Filter is global (`is_global=True`)
🌐 Unhighlighted globe	Filter is not global (`is_global=False`)

In Model Settings (FiltersSelector)

State	Checkbox	Description
Global Filter	✅ Checked & Disabled (greyed)	"This filter is globally enabled"
Selected Filter	✅ Checked & Enabled	"This filter is selected for this model"
Unselected Filter	☐ Unchecked & Enabled	"Click to include this filter"

Element	Description
Filter name	Shows the filter's display name
Custom icon	SVG icon from `self.icon` (if provided)
Toggle switch	Enable/disable the filter for this chat
Status badge	Shows if filter is currently active

💡 Best Practices for Filter Configuration

1. When to Use Global Filters

✅ Use global filters for:

Security and compliance (PII scrubbing, content moderation)
System-wide formatting (standardize all outputs)
Logging and analytics (track all requests)
Organization-wide policies (enforce company guidelines)

❌ Don't use global filters for:

Optional features (use toggleable filters instead)
Model-specific behavior (use model-specific filters)
User-preference features (let users control via toggles)

2. When to Use Toggleable Filters

✅ Make a filter toggleable (toggle=True) when:

Users should control when it's active (web search, translation)
It's an optional enhancement (citation mode, verbose output)
It adds functionality users may not always want (code formatting)
It has a performance cost that should be optional

❌ Don't make a filter toggleable when:

It's required for security/compliance (always-on is better)
Users shouldn't be able to disable it (use always-on)
It's a system-level transformation (global is better)

3. Organizing Filters for Your Organization

Recommended Structure:

Global Always-On Filters:
├─ PII Scrubber (security)
├─ Content Moderator (compliance)
└─ Request Logger (analytics)

Model-Specific Always-On Filters:
├─ Code Formatter (for coding models only)
├─ Medical Terminology Corrector (for medical models)
└─ Legal Citation Validator (for legal models)

Toggleable Filters (User Choice):
├─ Web Search Integration
├─ Citation Mode
├─ Translation Filter
├─ Verbose Output Mode
└─ Image Description Generator

🎯 Key Components Explained

1️⃣ `Valves` Class (Optional Settings)

Think of Valves as the knobs and sliders for your filter. If you want to give users configurable options to adjust your Filter’s behavior, you define those here.

class Valves(BaseModel):
    OPTION_NAME: str = "Default Value"

For example: If you're creating a filter that converts responses into uppercase, you might allow users to configure whether every output gets totally capitalized via a valve like TRANSFORM_UPPERCASE: bool = True/False.

You can enhance the user experience for your filter's settings by providing dropdown menus instead of free-form text inputs for certain Valves. This is achieved using json_schema_extra with the enum keyword in your Pydantic Field definitions.

The enum keyword allows you to specify a list of predefined values that the UI should present as options in a dropdown.

Example: Creating a dropdown for color themes in a filter.

from pydantic import BaseModel, Field
from typing import Optional

# Define your available options (e.g., color themes)
COLOR_THEMES = {
    "Plain (No Color)": [],
    "Monochromatic Blue": ["blue", "RoyalBlue", "SteelBlue", "LightSteelBlue"],
    "Warm & Energetic": ["orange", "red", "magenta", "DarkOrange"],
    "Cool & Calm": ["cyan", "blue", "green", "Teal", "CadetBlue"],
    "Forest & Earth": ["green", "DarkGreen", "LimeGreen", "OliveGreen"],
    "Mystical Purple": ["purple", "DarkOrchid", "MediumPurple", "Lavender"],
    "Grayscale": ["gray", "DarkGray", "LightGray"],
    "Rainbow Fun": [
        "red",
        "orange",
        "yellow",
        "green",
        "blue",
        "indigo",
        "violet",
    ],
    "Ocean Breeze": ["blue", "cyan", "LightCyan", "DarkTurquoise"],
    "Sunset Glow": ["DarkRed", "DarkOrange", "Orange", "gold"],
    "Custom Sequence (See Code)": [],
}

class Filter:
    class Valves(BaseModel):
        selected_theme: str = Field(
            "Monochromatic Blue",
            description="Choose a predefined color theme for LLM responses. 'Plain (No Color)' disables coloring.",
            json_schema_extra={"enum": list(COLOR_THEMES.keys())}, # KEY: This creates the dropdown
        )
        custom_colors_csv: str = Field(
            "",
            description="CSV of colors for 'Custom Sequence' theme (e.g., 'red,blue,green'). Uses xcolor names.",
        )
        strip_existing_latex: bool = Field(
            True,
            description="If true, attempts to remove existing LaTeX color commands. Recommended to avoid nested rendering issues.",
        )
        colorize_type: str = Field(
            "sequential_word",
            description="How to apply colors: 'sequential_word' (word by word), 'sequential_line' (line by line), 'per_letter' (letter by letter), 'full_message' (entire message).",
            json_schema_extra={
                "enum": [
                    "sequential_word",
                    "sequential_line",
                    "per_letter",
                    "full_message",
                ]
            }, # Another example of an enum dropdown
        )
        color_cycle_reset_per_message: bool = Field(
            True,
            description="If true, the color sequence restarts for each new LLM response message. If false, it continues across messages.",
        )
        debug_logging: bool = Field(
            False,
            description="Enable verbose logging to the console for debugging filter operations.",
        )

    def __init__(self):
        self.valves = self.Valves()
        # ... rest of your __init__ logic ...

What's happening?

json_schema_extra: This argument in Field allows you to inject arbitrary JSON Schema properties that Pydantic doesn't explicitly support but can be used by downstream tools (like Open WebUI's UI renderer).
"enum": list(COLOR_THEMES.keys()): This tells Open WebUI that the selected_theme field should present a selection of values, specifically the keys from our COLOR_THEMES dictionary. The UI will then render a dropdown menu with "Plain (No Color)", "Monochromatic Blue", "Warm & Energetic", etc., as selectable options.
The colorize_type field also demonstrates another enum dropdown for different coloring methods.

Using enum for your Valves options makes your filters more user-friendly and prevents invalid inputs, leading to a smoother configuration experience.

2️⃣ `inlet` Function (Input Pre-Processing)

The inlet function is like prepping food before cooking. Imagine you’re a chef: before the ingredients go into the recipe (the LLM in this case), you might wash vegetables, chop onions, or season the meat. Without this step, your final dish could lack flavor, have unwashed produce, or simply be inconsistent.

In the world of Open WebUI, the inlet function does this important prep work on the user input before it’s sent to the model. It ensures the input is as clean, contextual, and helpful as possible for the AI to handle.

📥 Input:

body: The raw input from Open WebUI to the model. It is in the format of a chat-completion request (usually a dictionary that includes fields like the conversation's messages, model settings, and other metadata). Think of this as your recipe ingredients.

🚀 Your Task: Modify and return the body. The modified version of the body is what the LLM works with, so this is your chance to bring clarity, structure, and context to the input.

🍳 Why Would You Use the `inlet`?

Adding Context: Automatically append crucial information to the user’s input, especially if their text is vague or incomplete. For example, you might add "You are a friendly assistant" or "Help this user troubleshoot a software bug."
Formatting Data: If the input requires a specific format, like JSON or Markdown, you can transform it before sending it to the model.
Sanitizing Input: Remove unwanted characters, strip potentially harmful or confusing symbols (like excessive whitespace or emojis), or replace sensitive information.
Streamlining User Input: If your model’s output improves with additional guidance, you can use the inlet to inject clarifying instructions automatically!
Rate Limiting: Track requests per user and reject requests that exceed your quota (works for both WebUI and API requests).
Request Logging: Log all incoming requests for analytics, debugging, or billing purposes.
Language Detection: Detect the user's language and inject translation instructions or route to a language-specific model.
Prompt Injection Detection: Scan user input for attempts to manipulate the system prompt and block malicious requests.
Cost Estimation: Estimate input tokens before sending to the model for budget tracking.
A/B Testing: Route users to different model configurations based on user ID or random selection.

💡 Example Use Cases: Build on Food Prep

🥗 Example 1: Adding System Context

Let’s say the LLM is a chef preparing a dish for Italian cuisine, but the user hasn’t mentioned "This is for Italian cooking." You can ensure the message is clear by appending this context before sending the data to the model.

def inlet(self, body: dict, __user__: Optional[dict] = None) -> dict:
    # Add system message for Italian context in the conversation
    context_message = {
        "role": "system",
        "content": "You are helping the user prepare an Italian meal."
    }
    # Insert the context at the beginning of the chat history
    body.setdefault("messages", []).insert(0, context_message)
    return body

📖 What Happens?

Any user input like "What are some good dinner ideas?" now carries the Italian theme because we’ve set the system context! Cheesecake might not show up as an answer, but pasta sure will.

🔪 Example 2: Cleaning Input (Remove Odd Characters)

Suppose the input from the user looks messy or includes unwanted symbols like !!!, making the conversation inefficient or harder for the model to parse. You can clean it up while preserving the core content.

def inlet(self, body: dict, __user__: Optional[dict] = None) -> dict:
    # Clean the last user input (from the end of the 'messages' list)
    last_message = body["messages"][-1]["content"]
    body["messages"][-1]["content"] = last_message.replace("!!!", "").strip()
    return body

📖 What Happens?

Before: "How can I debug this issue!!!" ➡️ Sent to the model as "How can I debug this issue"

note

Note: The user feels the same, but the model processes a cleaner and easier-to-understand query.

📊 How `inlet` Helps Optimize Input for the LLM:

Improves accuracy by clarifying ambiguous queries.
Makes the AI more efficient by removing unnecessary noise like emojis, HTML tags, or extra punctuation.
Ensures consistency by formatting user input to match the model’s expected patterns or schemas (like, say, JSON for a specific use case).

💭 Think of inlet as the sous-chef in your kitchen—ensuring everything that goes into the model (your AI "recipe") has been prepped, cleaned, and seasoned to perfection. The better the input, the better the output!

🆕 3️⃣ `stream` Hook (New in Open WebUI 0.5.17)

🔄 What is the `stream` Hook?

The stream function is a new feature introduced in Open WebUI 0.5.17 that allows you to intercept and modify streamed model responses in real time.

Unlike outlet, which processes an entire completed response, stream operates on individual chunks as they are received from the model.

🛠️ When to Use the Stream Hook?

Real-time content filtering - Censor profanity or sensitive content as it streams
Live word replacement - Replace brand names, competitor mentions, or outdated terms
Streaming analytics - Count tokens and track response length in real-time
Progress indicators - Detect specific patterns to show loading states
Debugging - Log each chunk for troubleshooting streaming issues
Format correction - Fix common formatting issues as they appear

📜 Example: Logging Streaming Chunks

Here’s how you can inspect and modify streamed LLM responses:

def stream(self, event: dict) -> dict:
    print(event)  # Print each incoming chunk for inspection
    return event

Example Streamed Events:

{"id": "chatcmpl-B4l99MMaP3QLGU5uV7BaBM0eDS0jb","choices": [{"delta": {"content": "Hi"}}]}
{"id": "chatcmpl-B4l99MMaP3QLGU5uV7BaBM0eDS0jb","choices": [{"delta": {"content": "!"}}]}
{"id": "chatcmpl-B4l99MMaP3QLGU5uV7BaBM0eDS0jb","choices": [{"delta": {"content": " 😊"}}]}

📖 What Happens?

Each line represents a small fragment of the model's streamed response.
The delta.content field contains the progressively generated text.

🔄 Example: Filtering Out Emojis from Streamed Data

def stream(self, event: dict) -> dict:
    for choice in event.get("choices", []):
        delta = choice.get("delta", {})
        if "content" in delta:
            delta["content"] = delta["content"].replace("😊", "")  # Strip emojis
    return event

📖 Before: "Hi 😊" 📖 After: "Hi"

4️⃣ `outlet` Function (Output Post-Processing)

The outlet function is like a proofreader: tidy up the AI's response (or make final changes) after it’s processed by the LLM.

📤 Input:

body: This contains all current messages in the chat (user history + LLM replies).

🚀 Your Task: Modify this body. You can clean, append, or log changes, but be mindful of how each adjustment impacts the user experience.

💡 Best Practices:

Prefer logging over direct edits in the outlet (e.g., for debugging or analytics).
If heavy modifications are needed (like formatting outputs), consider using the pipe function instead.

🛠️ Use Cases for `outlet`:

Response logging - Track all model outputs for analytics or compliance
Token usage tracking - Count output tokens after completion for billing
Langfuse/observability integration - Send traces to monitoring platforms
Citation formatting - Reformat reference links in the final output
Disclaimer injection - Append legal notices or AI disclosure statements
Response caching - Store responses for future retrieval
Quality scoring - Run automated quality checks on model outputs

Outlet and API Requests

Remember: outlet() is not called for direct API requests to /api/chat/completions. If you need outlet processing for API calls, see the Filter Behavior with API Requests section above.

💡 Example Use Case: Strip out sensitive API responses you don't want the user to see:

def outlet(self, body: dict, __user__: Optional[dict] = None) -> dict:
    for message in body["messages"]:
        message["content"] = message["content"].replace("<API_KEY>", "[REDACTED]")
    return body

🌟 Filters in Action: Building Practical Examples

Let’s build some real-world examples to see how you’d use Filters!

📚 Example #1: Add Context to Every User Input

Want the LLM to always know it's assisting a customer in troubleshooting software bugs? You can add instructions like "You're a software troubleshooting assistant" to every user query.

class Filter:
    def inlet(self, body: dict, __user__: Optional[dict] = None) -> dict:
        context_message = {
            "role": "system",
            "content": "You're a software troubleshooting assistant."
        }
        body.setdefault("messages", []).insert(0, context_message)
        return body

📚 Example #2: Highlight Outputs for Easy Reading

Returning output in Markdown or another formatted style? Use the outlet function!

class Filter:
    def outlet(self, body: dict, __user__: Optional[dict] = None) -> dict:
        # Add "highlight" markdown for every response
        for message in body["messages"]:
            if message["role"] == "assistant":  # Target model response
                message["content"] = f"**{message['content']}**"  # Highlight with Markdown
        return body

🚧 Potential Confusion: Clear FAQ 🛑

Q: How Are Filters Different From Pipe Functions?

Filters modify data going to and coming from models but do not significantly interact with logic outside of these phases. Pipes, on the other hand:

Can integrate external APIs or significantly transform how the backend handles operations.
Expose custom logic as entirely new "models."

Q: Can I Do Heavy Post-Processing Inside `outlet`?

You can, but it’s not the best practice.:

Filters are designed to make lightweight changes or apply logging.
If heavy modifications are required, consider a Pipe Function instead.

🎉 Recap: Why Build Filter Functions?

By now, you’ve learned:

Inlet manipulates user inputs (pre-processing).
Stream intercepts and modifies streamed model outputs (real-time).
Outlet tweaks AI outputs (post-processing).
Filters are best for lightweight, real-time alterations to the data flow.
With Valves, you empower users to configure Filters dynamically for tailored behavior.

🚀 Your Turn: Start experimenting! What small tweak or context addition could elevate your Open WebUI experience? Filters are fun to build, flexible to use, and can take your models to the next level!

Happy coding! ✨

🌊 What Are Filters in Open WebUI?​

🗺️ Structure of a Filter Function: The Skeleton​

🦴 Basic Skeleton of a Filter​

🆕 🧲 Toggle Filter Example: Adding Interactivity and Icons (New in Open WebUI 0.6.10)​

🖼️ What’s happening?​

⚙️ Filter Administration & Configuration​

🌐 Global Filters vs. Model-Specific Filters​

Filter Activation States​

Admin Panel: Making a Filter Global​

🎛️ The Two-Tier Filter System​

Tier 1: FiltersSelector (Which filters are available?)​

Tier 2: DefaultFiltersSelector (Which toggleable filters start enabled?)​

🔄 Toggleable Filters vs. Always-On Filters​

Always-On Filters (No toggle property)​

Toggleable Filters (toggle=True)​

📊 Filter Execution Flow​

📡 Filter Behavior with API Requests​

Key Behavioral Differences​

Triggering Outlet for API Requests​

Detecting API vs WebUI Requests​

Example: Rate Limiting for All Requests​

Example: Logging All API Usage​

⚡ Filter Priority & Execution Order​

Setting Filter Priority​

Priority Ordering Rules​

🔗 Data Passing Between Filters​

🎨 UI Indicators & Visual Feedback​

In the Admin Functions Panel​

In Model Settings (FiltersSelector)​

In Chat UI (Integrations Menu)​

💡 Best Practices for Filter Configuration​

1. When to Use Global Filters​

2. When to Use Toggleable Filters​

3. Organizing Filters for Your Organization​

🎯 Key Components Explained​

1️⃣ Valves Class (Optional Settings)​

Configuring Valves with Dropdown Menus (Enums)​

2️⃣ inlet Function (Input Pre-Processing)​

🍳 Why Would You Use the inlet?​

💡 Example Use Cases: Build on Food Prep​

🥗 Example 1: Adding System Context​

🔪 Example 2: Cleaning Input (Remove Odd Characters)​

📊 How inlet Helps Optimize Input for the LLM:​

🆕 3️⃣ stream Hook (New in Open WebUI 0.5.17)​

🔄 What is the stream Hook?​

🛠️ When to Use the Stream Hook?​

📜 Example: Logging Streaming Chunks​

🔄 Example: Filtering Out Emojis from Streamed Data​

4️⃣ outlet Function (Output Post-Processing)​

🛠️ Use Cases for outlet:​

🌟 Filters in Action: Building Practical Examples​

📚 Example #1: Add Context to Every User Input​

📚 Example #2: Highlight Outputs for Easy Reading​

🚧 Potential Confusion: Clear FAQ 🛑​

Q: How Are Filters Different From Pipe Functions?​

Q: Can I Do Heavy Post-Processing Inside outlet?​

🎉 Recap: Why Build Filter Functions?​

🌊 What Are Filters in Open WebUI?

🗺️ Structure of a Filter Function: The Skeleton

🦴 Basic Skeleton of a Filter

🆕 🧲 Toggle Filter Example: Adding Interactivity and Icons (New in Open WebUI 0.6.10)

🖼️ What’s happening?

⚙️ Filter Administration & Configuration

🌐 Global Filters vs. Model-Specific Filters

Filter Activation States

Admin Panel: Making a Filter Global

🎛️ The Two-Tier Filter System

Tier 1: FiltersSelector (Which filters are available?)

Tier 2: DefaultFiltersSelector (Which toggleable filters start enabled?)

🔄 Toggleable Filters vs. Always-On Filters

Always-On Filters (No `toggle` property)

Toggleable Filters (`toggle=True`)

📊 Filter Execution Flow

📡 Filter Behavior with API Requests

Key Behavioral Differences

Triggering Outlet for API Requests

Detecting API vs WebUI Requests

Example: Rate Limiting for All Requests

Example: Logging All API Usage

⚡ Filter Priority & Execution Order

Setting Filter Priority

Priority Ordering Rules

🔗 Data Passing Between Filters

🎨 UI Indicators & Visual Feedback

In the Admin Functions Panel

In Model Settings (FiltersSelector)

In Chat UI (Integrations Menu)

💡 Best Practices for Filter Configuration

1. When to Use Global Filters

2. When to Use Toggleable Filters

3. Organizing Filters for Your Organization

🎯 Key Components Explained

1️⃣ `Valves` Class (Optional Settings)

Configuring Valves with Dropdown Menus (Enums)

2️⃣ `inlet` Function (Input Pre-Processing)

🍳 Why Would You Use the `inlet`?

💡 Example Use Cases: Build on Food Prep

🥗 Example 1: Adding System Context

🔪 Example 2: Cleaning Input (Remove Odd Characters)

📊 How `inlet` Helps Optimize Input for the LLM:

🆕 3️⃣ `stream` Hook (New in Open WebUI 0.5.17)

🔄 What is the `stream` Hook?

🛠️ When to Use the Stream Hook?

📜 Example: Logging Streaming Chunks

🔄 Example: Filtering Out Emojis from Streamed Data

4️⃣ `outlet` Function (Output Post-Processing)

🛠️ Use Cases for `outlet`:

🌟 Filters in Action: Building Practical Examples

📚 Example #1: Add Context to Every User Input

📚 Example #2: Highlight Outputs for Easy Reading

🚧 Potential Confusion: Clear FAQ 🛑

Q: How Are Filters Different From Pipe Functions?

Q: Can I Do Heavy Post-Processing Inside `outlet`?

🎉 Recap: Why Build Filter Functions?