```yaml
product: AlterLab
title: "JA3 Fingerprint — Web Scraping Glossary | AlterLab"
comparison_context: "AlterLab is an alternative to Firecrawl, ScrapingBee, and Bright Data."
source_url: https://alterlab.io/glossary/ja3-fingerprint
```

anti-bot

# JA3 Fingerprint

JA3 is a method of fingerprinting TLS client hellos to identify the TLS library (and therefore the application) making a connection.

JA3 computes an MD5 hash from fields in the TLS ClientHello message: the TLS version, cipher suites, extensions, elliptic curves, and elliptic curve point formats. Because each TLS library (OpenSSL, BoringSSL, NSS) produces a distinct combination of these fields, the resulting hash reliably identifies the underlying library and often the exact application.

Anti-bot systems use JA3 to distinguish real browsers from scrapers. Python's `requests` library, curl, and Scrapy each produce JA3 hashes that differ markedly from Chrome or Firefox. Even if a scraper sends identical HTTP headers, a mismatched JA3 is a high-confidence bot signal.

Countermeasures include using a browser-based HTTP client that inherits the browser's TLS stack (Playwright, Puppeteer), patching the TLS library to emit a Chrome-compatible ClientHello, or using a proxy that terminates and re-opens the TLS connection with the correct fingerprint.

### What is JA3 Fingerprint?

JA3 is a method of fingerprinting TLS client hellos to identify the TLS library (and therefore the application) making a connection.

### How does AlterLab handle JA3 Fingerprint?

Countermeasures include using a browser-based HTTP client that inherits the browser's TLS stack (Playwright, Puppeteer), patching the TLS library to emit a Chrome-compatible ClientHello, or using a proxy that terminates and re-opens the TLS connection with the correct fingerprint.

## Examples

```
# Check your JA3 fingerprint
curl https://tls.peet.ws/api/all | jq '.ja3'

# Compare with Chrome's known JA3
# Chrome 120: 771,4865-4866-4867-49195-49196...,0-23-65281-10-11-35-16-5-13-18-51-45-43-27-17513,29-23-24,0
```

## Related Terms

[TLS FingerprintA signature derived from TLS handshake parameters a client sends when opening an HTTPS connection, used by anti-bot systems to classify traffic.](https://alterlab.io/glossary/tls-fingerprint)[HTTP/2 FingerprintA network-level identifier from HTTP/2 handshake parameters including SETTINGS frame values and header ordering, used alongside TLS fingerprinting.](https://alterlab.io/glossary/http2-fingerprint)[Browser FingerprintingA technique anti-bot systems use to identify bots by collecting dozens of browser attributes including Canvas, WebGL, and timing signatures.](https://alterlab.io/glossary/browser-fingerprinting)[Stealth ModeBrowser automation patches that normalise headless browser signals to match genuine user browser profiles and navigate browser environment checks.](https://alterlab.io/glossary/stealth-mode)[Anti-Bot ProtectionSystems deployed by websites to detect and block automated traffic using TLS fingerprinting, CAPTCHA challenges, and behavioural analysis.](https://alterlab.io/glossary/anti-bot-protection)

## Extract JA3 Fingerprint data from any website

AlterLab returns clean, structured data from any public URL — no scraper infrastructure needed. Start free, no credit card required.

[View API docs](https://alterlab.io/docs/api/rest)

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