# Web Bot Auth — verifiable bot identity > Source: > Published: 2026-09-10 00:00:00+00:00 # Web Bot Auth — verifiable bot identity Web Bot Auth lets a bot prove who it is by signing each HTTP request with a key it controls. Sites can then allow or block specific bots without IP allow-lists, user-agent strings, or guesswork. Built on RFC 9421 HTTP Message Signatures. ## What it is Web Bot Auth is an emerging convention that lets a bot prove its identity cryptographically on every request, using the standard [HTTP Message Signatures](https://www.rfc-editor.org/rfc/rfc9421) mechanism from RFC 9421. Instead of guessing whether a request really comes from OpenAI’s crawler by inspecting the user-agent string and looking up reverse DNS, the server reads a `Signature` header, fetches the bot’s public key from a published key directory, and verifies the signature. The work now has an IETF home. In September 2026 the [Web Bot Auth working group](https://datatracker.ietf.org/wg/webbotauth/about/) adopted [draft-ietf-webbotauth-httpsig-protocol](https://datatracker.ietf.org/doc/draft-ietf-webbotauth-httpsig-protocol/) as its first working-group document, folding in the separate key-directory draft that used to sit alongside it. One document now covers the trust model, the signing rules, the `Signature-Agent` header used to discover a bot’s keys, and the JWK Set that header points at — served, the draft asks IANA to register, from `/.well-known/http-message-signatures-directory`. Cloudflare ships verification at the network edge, and a growing list of major crawlers sign their traffic. Working-group adoption is not publication. The draft is still a draft, its details can and will change before it becomes an RFC, and the well-known URI it names is requested rather than registered. What adoption does tell you is that the mechanism is no longer one vendor’s proposal: it has a chartered group, chairs, and a deliverable date, so building against it is a bet on a process rather than on a company. ## Why it matters - **User-agent strings lie.** Anyone can set`User-Agent: GPTBot/1.0` . Signed requests cannot be forged without the bot operator’s private key. - **IP allow-lists rot.** Crawler IP ranges change. A signature-based check survives infrastructure migrations on the bot’s side. - **Granular policy.** Once you can verify the caller, you can apply different rules — paywall bypass for partner agents, slower rate limits for low-trust crawlers — without bespoke detection. - **Composable with [Content Signals](https://specification.website/spec/agent-readiness/content-signals/) and [robots.txt for AI crawlers](https://specification.website/spec/agent-readiness/robots-for-ai-crawlers/).** robots.txt declares the policy; Web Bot Auth proves the identity the policy is about to be applied to. Treat it as `optional` for now. The draft is pre-RFC, the verifier ecosystem is small, and most sites will get the benefit transparently via their CDN before they touch any code. But the direction is clear: bot identity is moving from “trust the header” to “verify the signature”. ## How to implement **If you are running a site:** - **Use a verifier that supports your signing profile.** Follow its documented identity result. If verification happens at a proxy, accept that result only over a trusted proxy-to-origin path; strip client-supplied copies of identity headers. - **Combine, do not replace.** Web Bot Auth tells you who is calling.[robots.txt](https://specification.website/spec/seo/robots-txt/) and[Content Signals](https://specification.website/spec/agent-readiness/content-signals/) tell you what they may do with the response. Both layers are needed. - **Keep authorisation separate.** A valid signature establishes a key/identifier association, not permission or good behaviour. Apply your own policy to verified identifiers and retain your existing defaults for unsigned traffic. **If you operate a bot:** - **Generate an asymmetric signing keypair.** The draft restricts you to algorithms in the RFC 9421 registry and rules out shared-secret HMAC outright — a symmetric key would have to be handed to every site that wants to verify, which defeats the point. - **Publish the public key** as a JWK Set. For default directory discovery, serve it at`https://bot.example/.well-known/http-message-signatures-directory` with media type`application/http-message-signatures-directory+json` . Send`Signature-Agent: sig1="https://bot.example"` : the value is an HTTPS**origin** , not the well-known file’s URL. For a direct JWK Set URL instead, send`Signature-Agent: sig1="https://bot.example/keys.json";type=jwks_uri` . - **Use the same label** (`sig1` here) in`Signature` ,`Signature-Input` and`Signature-Agent` . Cover the matching dictionary member with`"signature-agent";key="sig1"` in`Signature-Input` , alongside the required target component. See[draft sections 5.2.1 and 5.5](https://datatracker.ietf.org/doc/html/draft-ietf-webbotauth-httpsig-protocol-00#section-5.2.1) . - **Sign every request** with`Signature` and`Signature-Input` per RFC 9421, covering`@authority` or`@target-uri` and carrying the`created` ,`expires` ,`keyid` , and`tag` parameters.`tag` must be`web-bot-auth` , which is what lets a verifier tell this profile apart from other uses of message signatures on the same connection. - **Rotate keys** without breaking verifiers: allow for cached directories and outstanding signatures when overlapping keys; remove compromised keys promptly. ## Common mistakes - Blocking unsigned traffic as a default. The standard is opt-in for bots; legitimate non-signing clients (including most browsers) will be locked out. - Skipping `created` and`expires` , or accepting stale timestamps. Both are mandatory signature parameters in the draft; without a freshness window a captured signature replays forever. - Verifying only the homepage. Bots fetch internal pages too; the policy has to apply site-wide. - Assuming a signature authenticates `User-Agent` . It protects only the components it covers; the profile does not require that header to be signed. ## Verification - Send an actually signed request using your signing client. Confirm the verifier reports the expected identifier, then change a covered component and confirm verification fails. Placeholder signature values cannot test success. - For bot operators: feed your signed request into an RFC 9421 verifier and confirm the canonicalised signature base matches what your client constructed. - Check your access logs for a verified-bot tag on traffic from signing crawlers (OpenAI, Anthropic, Perplexity, and others publish their key sets). ## Related topics ## Sources & further reading - [RFC 9421 — HTTP Message Signatures](https://www.rfc-editor.org/rfc/rfc9421) — IETF - [draft-ietf-webbotauth-httpsig-protocol — HTTP Message Signatures for automated traffic](https://datatracker.ietf.org/doc/draft-ietf-webbotauth-httpsig-protocol/) — IETF Web Bot Auth Working Group - [IETF Web Bot Auth (webbotauth) Working Group](https://datatracker.ietf.org/wg/webbotauth/about/) — IETF - [Cloudflare — Forget IPs: using cryptography to verify bot and agent traffic](https://blog.cloudflare.com/web-bot-auth/) — Cloudflare