When a connection to an https site starts, the program lists the encryption methods it supports, in a certain order. Each browser and each library has its own recognisable list. A site can read it before any page is requested.
A script that claims to be Chrome in its user agent but opens connections like a Python library contradicts itself. A proxy passes the encrypted connection through unchanged, so it cannot fix this. A real browser, or a client built to copy one, can.
This is one reason a plain script can be blocked on its very first request, before it has done anything suspicious, even through a residential address. Tools that drive a real browser, such as Playwright, connect the way that browser does and do not have the problem.
Questions about TLS fingerprint
What is JA3?
A well-known way of writing a TLS fingerprint as a short code. Sites and security services compare it with the codes that real browsers produce.
Can a proxy change my TLS fingerprint?
No. The encrypted connection is made by your program and passes through the proxy unchanged. Only the program that makes the connection can change how it looks.
Related terms
- Browser fingerprint
- A browser fingerprint is the mix of details a browser reveals, such as screen size, fonts and graphics card, that together single it out.
- Bot detection
- Bot detection is the set of checks a website runs to tell people from programs: the IP address, the browser fingerprint and the behaviour.
- HTTPS through a proxy
- Yes. An HTTP proxy opens https sites through a tunnel, using a request called CONNECT. The traffic inside stays encrypted end to end.
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