Track AI assistant traffic

AI assistants like ChatGPT, Claude, and Perplexity fetch web pages, but they don't run the site tag, so the tag never sees them. A small file on your site records each fetch in your PostHog project. Performance then shows the hits in its AI assistant traffic section.

A hit means an assistant fetched a page. It doesn't mean the assistant cited or recommended you.

Before you start

• The site runs Next.js 16 or later. Other site builders aren't supported yet.
• PostHog is connected in Connections > PostHog. Without it, the site shows "Connect PostHog" instead of the file.

Install the file

1. Open Settings > Websites.
2. Pick the website from the menu on its name if you have more than one.
3. Under AI assistant tracking, select Copy on the file.
4. Save it as proxy.ts at the root of the site's project and deploy. If the site already has a proxy.ts, the comment at the top of the file says how to merge the two.

The file already holds your PostHog project's public token, the same one the site tag uses. Copy a fresh file from Mark rather than editing it by hand.

Check the install

Select Check AI assistant tracking. Mark loads the site's home page as Mark-Probe, then waits up to 30 seconds for that visit to reach PostHog. Mark-Probe is Mark's own check. It never counts as an assistant.

Each website keeps its own last result under the button, with the time Mark checked. If the page says The check didn't finish, Mark has no result for that run; select the button again.

Let assistants and Mark-Probe through your firewall

A firewall in front of your site runs before the tracking file. When it blocks a request, the file never sees it and no hit is recorded. Mark's check only tests Mark-Probe, so a firewall can block real assistants while the check still says Installed. If Performance shows no hits for weeks, check the firewall first.

Let these user agents through: GPTBot, OAI-SearchBot, ChatGPT-User, ClaudeBot, Claude-SearchBot, Claude-User, PerplexityBot, Perplexity-User, and Mark-Probe. Rules that match on a user agent let in anyone who sends that name, so allow only these.

Vercel Firewall

1. Open the site's project in Vercel and select Firewall.
2. Select Configure, then Add New > Rule.
3. Under If, pick User Agent, choose a contains operator, and enter Mark-Probe. Add one condition per assistant name, joined with OR.
4. Under Then, pick Bypass.
5. Select Save Rule, then Review Changes and Publish.
6. Drag the rule above any rule that denies or challenges traffic.

A Bypass rule gets a request past your other custom rules and past Bot Protection. Under Bot Management, keep AI Bots Ruleset on Allow. Attack Mode lets known bots through, but it may still challenge Mark-Probe, so check again after you turn it off.

Cloudflare

1. In Security Settings, open Configure AI bot policies. Set Search and Agent to Allow (do not block). Agent covers ChatGPT-User, Claude-User, and Perplexity-User, which fetch a page when a person asks about it. Training covers GPTBot and ClaudeBot; allow it if you want to count those too.
2. If you use AI Crawl Control, open Crawlers and set each assistant to Allow.
3. On the Free plan, turn off Bot fight mode under Security Settings > Bot traffic. Cloudflare doesn't let a rule skip it.
4. On Pro and above, add a skip rule instead. Open Security rules > Create rule > Custom rules, enter the expression http.user_agent contains "Mark-Probe", pick Skip, and select All Super Bot Fight Mode rules, All managed rules, and All remaining custom rules. Add the assistant names with or. Place the rule first.

Arcjet

Arcjet's rules live in your site's code, not a dashboard.

• In detectBot, add "CATEGORY:AI" to allow. It covers all eight assistants.
• Arcjet has no allow entry for Mark-Probe. Mark-Probe only loads your home page, so skip protect when the path is / and the user agent contains Mark-Probe. Or run the tracking file before Arcjet in your proxy, which records the hit even when Arcjet then denies the request.

After you change a firewall, select Check AI assistant tracking again.

Read AI assistant traffic

Open Performance and pick a range. The AI assistant traffic section shows:

• Hits: every assistant fetch in the range, split into Verified and Unverified.
• Hits, verified, and unverified per assistant, split by kind:
  • Crawler collects pages for training or an index (GPTBot, ClaudeBot, PerplexityBot).
  • Search builds the assistant's own search results (OAI-SearchBot, Claude-SearchBot).
  • User fetch loads a page because a person asked the assistant about it (ChatGPT-User, Claude-User, Perplexity-User).
• Top pages: the 10 pages fetched most.
• A "Data through" line with the newest hit.

With no hits in the range, the section says so and links to the Website connection.

Select a path in Top pages to see that one page. Each assistant gets a row with its hits on the page in the range and the date of its newest fetch, or "None in range". Pick a 30-day range to see which assistants haven't fetched the page in 30 days. All pages goes back, and the range and filters stay as you set them. The one-page view shows hits only, not verified and unverified.

A hit counts when the request's user agent names an assistant. Anyone can send a request that claims to be GPTBot, so Mark also checks where it came from.

Verified and unverified hits

OpenAI, Anthropic, and Perplexity each publish the IP addresses their bots use. A hit is verified when it came from an address on the list for its assistant. Mark reloads the lists once a day.

A hit is unverified when Mark can't match it to a list. That happens when:

• Someone sent a fake assistant user agent.
• The request had no IP address.
• The vendor's list couldn't be loaded. The section says so. Mark checks the same hits again once the list loads.
• The site's PostHog project has Discard client IP data turned on. Every hit is then unverified.

Anthropic publishes one list for all its bots. A verified ClaudeBot, Claude-SearchBot, or Claude-User hit came from Anthropic, but the list can't show which of the three sent it. OpenAI and Perplexity publish a list per bot.

Verified doesn't mean the assistant cited or recommended your site. It only means the fetch really came from that company.