HTML Chat

A browser chat client for any OpenAI-compatible API, built into a single index.html file. It has no backend and no account. Everything, including your API key, is stored in your browser's IndexedDB.

Features:

• Streaming chat with reasoning display (reasoning_content / reasoning fields, inline <think> tags, LiteLLM thinking_blocks)
• Tool calling: JavaScript execution in the page, and semantic search over your own files (RAG)
• Editing, retrying, forking and deleting any message, and changing its role
• Markdown, syntax highlighting and KaTeX math
• Import and export of chats and embedding vectors
• Light and dark themes, with keyboard-driven navigation

Getting started

Use the prebuilt file

Open index.html in a browser. That's it.

Build from source

npm install
npm run dev      # dev server with hot reload
npm run build    # writes a self-contained index.html to the repo root

Connect

1. In the sidebar, set Base URL (e.g. https://api.openai.com/v1, http://localhost:11434/v1) and API Key.
2. Models are fetched from {Base URL}/models. If your server doesn't implement that endpoint, add model ids under Extra Models (see Advanced settings).
3. Pick a model and type your prompt. Ctrl+Enter sends.

The API server must allow cross-origin requests from the browser (CORS). Local servers often need this enabled explicitly.

Chatting

Action	How
Send	Ctrl/Cmd+Enter or Send
Add a message without calling the API	Ctrl+Shift+Enter, or Shift+Click Send
Stop generation	Click the send button while it's running
Set reasoning effort	Ctrl+Click the model dropdown, then pick a level. The level list is editable, one per line. none sends no reasoning_effort.

The Send button shows an estimate of the context size, at about 4 characters per token. It covers the full request, including tool definitions.

Message actions

Hover a message to see its buttons:

• Retry
  • On a user message: resends it and discards everything after it.
  • On a thinking box: resumes the turn from that point.
• Copy: copies the message as markdown.
• Edit: edits part of the message (see below).
• Fork: creates a new chat containing everything up to and including this message.
• Delete: removes the message.
• Role dropdown: switches a message between user, assistant and system.

Editing part of a message

After clicking Edit, click the block (paragraph, list, code block, etc.) you want to change. Its source loads into the composer, and a dotted outline marks it. Only one block is selected at a time.

• Clicking another block switches the selection to it.
• Clicking the selected block again deselects it.
• Save (Ctrl+Enter) writes the edit back. An empty composer deletes the selected block.
• Retry saves the edit and regenerates from the message.

Thinking boxes

Everything the model does before its answer is grouped into one collapsible box per turn: reasoning, text written alongside tool calls, and the tool calls with their results. The header shows how long you waited. Click any tool call to see its code or query and its result.

Tools

JavaScript execution

Tick Execute JavaScript to offer the model the run_javascript tool. The code runs inside this page, with full access to window, document, fetch and the app's own storage, which includes your API key. Only enable it with models and prompts you trust.

Calls run one at a time. Results are capped by Max Tool Result Tokens.

File search (RAG)

1. Set Embeddings Model in Advanced settings. File search is disabled without one.
2. Click Upload to add files. Indexing starts automatically in the background, with a progress bar and ETA.
3. Click a file's name to attach it to the current chat. Attached files are bold.

When a chat has files attached, the model gets a search_files tool:

• Your query is embedded and scored against every attached file's chunks by cosine similarity.
• The best matches from all files compete for one Max RAG Tokens budget.
• Each file's selected passages are put back in document order, merged and wrapped before being returned to the model.
• The model is told when a file isn't fully indexed yet.

File actions:

Action	How
Attach or detach	Click the name
Replace contents	Alt+Click the name
Per-file RAG settings	Ctrl+Click the file

Changing the embeddings model deletes all stored vectors, and every file must be re-indexed.

Per-file RAG settings

Ctrl+Click a file to open its settings. The toolbar has:

• Attempt Chunking: runs the chunker and writes its output into Custom Chunks so you can hand-edit it.
• Start / Pause Embedding
• Export / Import Vectors: a JSON file of chunks plus base64 vectors. Import requires the same embeddings model.

The per-file settings are:

Setting	Purpose
File Content Text	Edit the stored file text directly
File Wrapper Function	Overrides the global wrapper for this file
Max RAG Tokens	Cap on what this file can contribute to one search
RAG Match Threshold	Minimum similarity, from 0 to 1
Max Tokens Per Chunk	Chunks larger than this are skipped when embedding
Custom Chunks (JSON)	An array of strings or objects that bypasses the chunker entirely
Custom Chunking Function	Default: 1000-character chunks with 200-character overlap
Retrieval Function	Step 1: process or expand each retrieved chunk. Return null to drop it
Deduplication Function	Step 2: return true if currentData duplicates existingData
Merge Chunks Function	Step 3: combine the final chunks into one string

All the functions above are bodies of async JavaScript functions. They must return a value. Available variables:

Function	Variables
Chunker	fileContents, config
Retrieval	chunk, fileContents
Deduplication	currentData, existingData
Merge	finalChunks
Wrapper	fileContent, fileName

Chunks can be objects. Objects are JSON-stringified for embedding, and the original object is passed to your retrieval and merge functions.

Advanced settings

Open them with Ctrl+Click on the Settings heading, or Alt+I.

To change a setting, select it, edit the value in the bottom textarea, and save with Save or Ctrl+Enter. Reset restores one setting's default, and Reset All restores every default. Leaving a value blank uses the default.

Setting	Default	Notes
Temperature, Top P, Max Tokens, Frequency and Presence Penalty	API default	Sent only when set
Max Tool Rounds	10	After this many rounds, the model must answer without tools
Max Tool Result Tokens	4000	Truncates JavaScript results. 0 disables the cap
Echo Reasoning Field	off	reasoning_content or reasoning. Sends plain-text reasoning back during a tool loop, for models that need it. Signed thinking blocks are always sent back
JavaScript and File Search Tool Descriptions	built-in	What the model is told about each tool
Embeddings Base URL / API Key	chat URL / key	For a separate embeddings provider
Embeddings Model	—	Required for file search
Extra Models	—	Comma-separated. Always added to the model dropdown
File Wrapper Function	filename + fenced block	How each file's passages are presented to the model
Max RAG Tokens	5000	Total budget per search, across all files
RAG Match Threshold	0.0	Minimum similarity
Max Tokens Per Chunk	1024
Chunk Batch Size / Batch Max Tokens	100 / 8192	Per embeddings request
Collapse Thinking	true	Whether new thinking boxes start closed
Auto-Collapse Code, Threshold, Preview Lines, Hint	true, 20, 5, true	Long code blocks fold. Click to toggle
Max Visible Chats / Files	unlimited	Limits sidebar list height

Keyboard and mouse

Shortcut	Action
Alt+T	New chat
Alt+W	Delete current chat
Alt+R	Rename current chat
Alt+↑ / Alt+↓	Previous / next chat
Alt+P	Toggle sidebar
Alt+O	Toggle title
Alt+D	Toggle dark mode
Alt+I	Advanced settings
Shift+↑ / Shift+↓	Jump between messages
↑ / ↓	Scroll the chat (outside text fields)
Ctrl+Click code, inline code or math	Copy it. Math copies as LaTeX source
Ctrl+Click a chat	Copy its transcript as markdown (without reasoning)
Alt+Click a chat	Export that chat as JSON
Alt+Click New	Import chats

Import and Export in the sidebar handle all chats as a single JSON file. Import skips chats whose id already exists.

Notes

• Markdown output is not sanitised. HTML in model output renders as HTML.
• All data lives in this browser's IndexedDB. Clearing site data deletes your chats, files, vectors and key. Use Export to back up.
• Token counts are estimates, at 4 characters per token.

License

See LICENSE.