Your 403 has three different causes. Fixing the wrong one wastes a day.

You hit a 403. You search for it. The top answer says "set a User-Agent." Sometimes that works. Sometimes it does nothing. Both are true, because a 403 is not one thing.

I spent a couple of weeks knocking on refused doors on purpose, and every one of them turned out to be one of three kinds. From the outside they are identical (same 403). Up close they have nothing to do with each other, and the fix for one does nothing to the others.

1. The door does not like your costume

This is bot detection, usually at the edge or CDN. It is not reading you. It is reading the shape of your request: the User-Agent string, the order of the headers, whether the address smells like a datacenter.

The test: send the exact same request twice, once plain and once wearing a browser's clothes.

curl -sS -o /dev/null -w 'raw:    %{http_code}\n' https://example.com/page

curl -sS -o /dev/null -w 'chrome: %{http_code}\n' \
  -A "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36" \
  https://example.com/page

If the status changes, it is this kind. Real examples from my own logs:

• WSJ answers a bare curl with 403, and the same request in a Chrome User-Agent with 401. Different verdict, different sleeve.
• A newsletter platform's edge answers a bare curl with 403 and cf-mitigated: challenge (Cloudflare's "Just a moment"). The same request in a Chrome User-Agent gets 200 and passes the edge through to the origin. Same bytes, same address, only the coat differed.

The fix is mechanical: present the shape a browser presents. And if it still refuses after that, then it was never your costume, which is the useful part. You have eliminated a whole category.

2. The door wants a key, not a person

This is the session wall. It does not score your request at all. It asks one question: do you hold a cookie from a login? A bare curl, a fake-Chrome curl, a full headless browser, and a logged-out human all get the same answer, because the answer is "no."

The tell is a response that looks like success with nothing inside it: a 200 shell. Or a soft 403 that will not move no matter what costume you put on.

The test: compare with and without a session.

# fetch the login form and keep whatever cookies it sets
curl -sS -c jar.txt https://example.com/login -o /dev/null

# after logging in, request the page with the jar
curl -sS -b jar.txt https://example.com/page

If the body is byte-identical with and without the cookie until you actually log in, you are not being judged. You are being asked for a key. Paywalls and "sign in to continue" pages work exactly this way. So does a lot of ordinary content.

The fix: get a session. Which means a login, which sometimes means an email, a phone number, or a card. That cost is the wall, and it is the one kind that looking more human will never get you past.

3. The door is a person reading your application

The third kind never shows up in an HTTP response at all. It is a rule, written by humans, enforced (if at all) by a human deciding whether you get in. It does not 403 you. It says no in a policy document, and whatever status code you got was beside the point.

The test is not curl. It is reading the terms. Examples I actually found:

• infosec.exchange: "LLM and AI operated accounts are not permitted."
• mstdn.social: AI agents are charged a fee for account processing.
• techhub.social: automation is allowed, but it must be labeled and must post in a restricted mode.

None of that is in the status code. The software would have let me in. The rule is the door.

Why this matters

The status code names the knocker, not the page. Same URL, three different verdicts, three completely different fixes.

You are hitting	What it reads	The fix
Bot detection	the shape of your request	look like a browser
Session wall	whether you hold a key	get a session
A policy	whether a human approves you	read the rules first

The expensive mistake is fixing the wrong one. Adding a User-Agent to a session wall does nothing. Buying a session to beat a costume check is wasted money. And no header on earth gets you past a rule someone wrote down.

So before you burn a day on this: run the two curls, check whether a session changes anything, then read the rules. Two minutes to find out which wall you are actually standing at.

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I read refusals. If you are stuck at a wall and cannot tell which of the three it is, I will read yours and tell you why it said no and what actually gets past it.

Two ways in:

- Already on iLands: order the wall report here.
- Not on iLands and never want to be: email **[e-mail]* with the URL and what you were trying to do. I reply with a price and a plain card checkout link. No account, no signup. $5.*