HuggingChat: Web Search, User Agents and Status
HuggingChat is a chat app from Hugging Face that runs open models from many providers. Hugging Face closed it on July 1, 2025, and brought it back on October 16, 2025. It searches the web through Exa, and it fetches pages that users attach by URL with its own user agent.
Status: closed in 2025, then back
On July 1, 2025, Hugging Face announced that HuggingChat was “closing for now”. The post said that the app closed to make room for something new that is more closely tied to the rest of Hugging Face.
On October 16, 2025, Hugging Face announced HuggingChat Omni with the words “HuggingChat returns”. The app is at huggingface.co/chat. Omni is a router that picks a model for each message. The models run through Hugging Face Inference Providers.
HuggingChat is open source. Its code is the chat-ui repository on GitHub.
Web search through Exa
HuggingChat gets its tools from MCP servers. MCP (Model Context Protocol) is a standard way to connect tools to an AI app. The production configuration of HuggingChat lists two base MCP servers: “Web Search (Exa)” and “Hugging Face”. The MCP tools documentation says that users can turn base servers on or off.
Web search requests go to Exa, a search API company. Exa documents two user agents. A user agent is the client name in the User-Agent HTTP header.
| User agent | Use, as Exa describes it | robots.txt |
|---|---|---|
ExaSearchBot |
Crawls and indexes public pages for Exa search | Follows a group for ExaSearchBot, then the rules for major search engines, then * |
ExaUser |
Fetches a page live when a user or an Exa API app asks for it | Exa says that robots.txt rules do not always apply |
These are the full strings from the ExaSearchBot page and the ExaUser page:
Mozilla/5.0 (compatible; ExaSearchBot/1.0; +https://crawler.exa.ai/)
Mozilla/5.0 (compatible; ExaUser/1.0; +https://crawler.exa.ai/exauser)Exa signs the requests of both agents with Web Bot Auth, which uses HTTP Message Signatures (RFC 9421). The public keys are at https://crawler.exa.ai/.well-known/http-message-signatures-directory. A signature is stronger proof than a user agent, because any client can copy a user agent. For more about Exa, see the Exa AI guide.
Hugging Face does not document how HuggingChat shows sources from these tools.
Pages that users attach by URL
A user can attach a file or page to a chat by its URL. The HuggingChat server fetches it with this user agent, as set in the chat-ui source code:
HuggingChat-Attachment-Fetcher/1.0The code accepts only HTTPS URLs, follows at most five redirects and stops at 10 MB. It does not read robots.txt. Hugging Face publishes no IP list for these requests.
Block or allow HuggingChat traffic
If you want to block URL attachments, block the HuggingChat-Attachment-Fetcher user agent on your web server, CDN or firewall. If you want to keep your pages out of Exa search, add this group to your robots.txt file:
User-agent: ExaSearchBot
Disallow: /Exa says that robots.txt controls crawling, not indexing. To remove a page that is already in the Exa index, Exa says to use a noindex robots meta tag. An X-Robots-Tag: noindex header also works. ExaSearchBot drops the page the next time that it fetches it.