Web UI

llama.cpp ships a modern chat interface built right into llama serve, with support for multimodal input, MCPs and more.

Getting started

Start the server with a model and open it in your browser:

llama serve -hf ggml-org/gemma-4-e4b-it-GGUF:Q4_0 -c 0

Then visit http://localhost:8080 to start chatting. If the server cannot bind to 8080, pass another port with port --8081.

A few launch tips:

• -c 0 uses the model’s full context window.
• Users can override parameters per conversation in the settings panel.
• To reach the WebUI from other devices on your network, add --host 0.0.0.0 (e.g. serving a model remotely accessing WebUI on your laptop).

Chatting

The chat interface streams responses in real time and renders rich output:

• Markdown: with tables, lists, and syntax-highlighted code blocks.
• Math: LaTeX expressions rendered with KaTeX.
• Reasoning: thinking models show their reasoning in a collapsible block, separate from the answer. You can toggle the visibility of this in settings.
• HTML/JS preview: generated web code can be rendered inline for immediate visualization.

Attachments

Add files to the conversation with media dropdown or drag-and-drop:

• Images/PDFs for vision language models (JPEG, PNG, GIF, WebP, SVG, PDF)
• Audio MP3/WAV for models that accept audio input

The UI knows each model’s capabilities and prevents sending e.g. an image to a text-only model.

Managing conversations

• Branching: edit any earlier message or regenerate any response to fork the conversation at that point, navigate between branches freely, nothing is lost
• Search: find conversations by title or content
• Import/Export: back up or share conversations as JSON files

Structured output

In the settings you can supply a custom JSON schema to constrain the model’s responses, handy for tasks like invoice extraction or data parsing where you need machine-readable output every time.

In the WebUI: Settings → Developer → Custom JSON, and put your schema:

{
	"json_schema": {
		"type": "object",
		"properties": {
			"sentiment": { "type": "string", "enum": ["positive", "neutral", "negative"] },
			"confidence": { "type": "number", "minimum": 0, "maximum": 1 },
			"summary": { "type": "string", "maxLength": 200 }
		},
		"required": ["sentiment", "confidence", "summary"]
	}
}

Multiple models

When the server runs in router mode (started without a model), the UI shows a model selector with loaded and available models. Selecting a model loads it automatically, and you can even switch models mid-conversation when regenerating a response.

Customization

Default UI preferences can be set at launch with --ui-config (below will turn theme into dark one, render user message with markdown and turns long message into a file attachment.)

llama serve -hf ggml-org/gemma-4-e4b-it-GGUF:Q4_0 --ui-config '{"theme": "dark", "pasteLongTextToFileLen": 0, "renderUserContentAsMarkdown": true}'

For the story behind the interface and more usage examples, see the WebUI guide discussion on GitHub.