Perplexity-User is operated by Perplexity. Fetches your page because a human asked an assistant to open it right now. Blocking it breaks a live request.
Perplexity runs it as a user-triggered fetcher, which means it fetches one page at the moment a person asks an assistant to open it. There is no index and no schedule: somebody has pasted your link or asked for your site by name, and is waiting for the answer while the request happens.
What blocking it costs you: Live user-requested fetches from Perplexity fail. A link somebody pasted into an assistant fails while they are watching. They asked for your page by name and got an error.
The user agent, and the token a rule matches on
These are two different strings and confusing them is why a rule that looks right does nothing.
A robots.txt rule matches on the product token, case-insensitively, and
ignores the rest of the user-agent header entirely.
An empty Disallow: and Allow: / mean the same thing to a crawler. What does
not mean the same thing is having no rule at all: absence is permission by default, but it is
permission nobody wrote down, and it survives only until somebody adds a blanket
User-agent: * block without thinking about this crawler.
Blocking Perplexity-User
User-agent: Perplexity-User
Disallow: /
Before you paste that: live user-requested fetches from Perplexity fail. That is the cost, and it is paid silently — no error appears in your logs, no report tells you, and the traffic you lose was traffic you never saw arrive.
How the web actually treats Perplexity-User
Measured on 2026-09-06, by reading the robots.txt of
292 public websites and resolving each one against this crawler specifically.
Verdict
Sites
Share
Blocked
23
8%
Explicitly allowed
215
74%
No rule either way
54
18%
No site is named, here or anywhere else on this domain. The count is the useful part; a league table of
businesses that never asked to be measured is not.
The row worth reading twice is the last one. 54 of 292 sites have written no rule about
Perplexity-User at all, which means their position on it is an accident rather than a decision — whatever
their User-agent: * block happens to say.
What Perplexity-User is not
Perplexity runs another crawler with
a different job, and this is where the expensive mistake happens.
Somebody means “do not train on my content”, writes one rule against the operator’s name as they
remember it, and blocks the crawler that would have sent them a customer instead.
Indexes you so an assistant can cite and link you. Blocking it removes you from AI answers.
Rules are matched per token. Blocking one of these says nothing about the others, which is the point:
you can refuse training and keep every crawler that puts your link in front of a person.
Checking what your site does right now
Reading your own robots.txt is not the same as knowing what a crawler concludes from it.
Precedence between a User-agent: * group and a named one, the longest-match rule between
overlapping paths, and a token you spelled slightly wrong all produce a file that looks correct and
behaves otherwise.
npx axray-cli your-site.com
The scan resolves your file against all 54 crawlers on this list individually and reports
which ones are allowed, blocked, or covered by nothing. It is free, needs no account, and installs nothing.
Questions people ask about Perplexity-User
What is Perplexity-User?
Perplexity-User is a user-triggered fetcher operated by Perplexity: it fetches one page at the moment a person asks an assistant to open it. There is no index and no schedule: somebody has pasted your link or asked for your site by name, and is waiting for the answer while the request happens.
Should I block Perplexity-User in robots.txt?
Only if you are willing to pay what it costs. Live user-requested fetches from Perplexity fail. A link somebody pasted into an assistant fails while they are watching. They asked for your page by name and got an error.
What is the Perplexity-User user agent string?
Mozilla/5.0 (compatible; Perplexity-User/1.0; +https://perplexity.ai/perplexity-user) — and the robots.txt product token, which is what a rule actually matches on, is Perplexity-User.
How do I check whether my site is blocking Perplexity-User right now?
Scan your site with AXRAY. It resolves your robots.txt against 54 named AI crawlers individually rather than reporting one verdict for all of them, so it will tell you whether this specific crawler is allowed, blocked, or covered by no rule at all. It is free and needs no account.