HTTP Header Checker - Request Headers & TLS Fingerprint

HTTP Header Checker

This HTTP header checker shows the request and response headers your client sends, and can display TLS fingerprint (e.g. JA3) so you can debug anti-bot and browser fingerprinting issues.

How to use

1. Enter a URL or use the default test endpoint.
2. Optionally set a custom User-Agent.
3. Click Check. View response headers and, when available, TLS fingerprint.

Why it matters for scraping

• See exactly what headers your scraper sends.
• Compare with real browsers to avoid fingerprint detection.
• Troubleshoot Cloudflare and other anti-bot blocks.

Headers that often trigger blocks

• User-Agent — Default library User-Agents (e.g. Python-requests/2.x) are easy to detect. Use a realistic browser User-Agent; see our User-Agent Generator.
• Accept-Language, Accept-Encoding — Missing or inconsistent with User-Agent can look bot-like. Real browsers send a predictable set.
• Sec-CH-UA, Sec-CH-UA-* (client hints) — Modern Chrome sends these; their absence or wrong values can contribute to fingerprinting. Read Browser Fingerprinting Explained and Browser Stealth Techniques for Scraping.

TLS fingerprint (JA3)

TLS fingerprinting identifies the client by how it performs the TLS handshake. Many anti-bot systems (including Cloudflare) use it. Scripts and non-browser HTTP clients often have a distinct JA3 and get challenged. Using a real browser (e.g. Playwright) with your proxy typically fixes this; see Bypass Cloudflare for Web Scraping.

Typical header sets by client type

• Python requests — Often sends User-Agent: Python-requests/x.x, minimal Accept headers. Easy to fingerprint. Use a custom User-Agent (e.g. from our User-Agent Generator) and set Accept, Accept-Language to match; see Using Requests for Web Scraping.
• Node / axios — Similar to requests; default User-Agent is node-specific. Customize for scraping; Web Scraping with Node.js has examples.
• Playwright / Puppeteer — Sends full browser-like headers and client hints. TLS fingerprint matches Chrome. Best for strict sites; Headless Browser Scraping Guide and Bypass Cloudflare for Web Scraping.

What to fix when your headers look “bot-like”

If the checker shows missing or inconsistent headers: (1) Set a realistic User-Agent (e.g. Chrome on Windows) using our User-Agent Generator. (2) Add Accept, Accept-Language, and Accept-Encoding similar to that browser. (3) For the strictest sites, use a real browser (Playwright) so TLS and all headers match. Browser Stealth Techniques for Scraping and Preventing Scraper Fingerprinting go deeper.

When to use a real browser instead of fixing headers

If you set a browser-like User-Agent and Accept headers but still get blocked, the site may be checking TLS fingerprint (JA3), JavaScript execution, or canvas/WebGL. Scripts (requests, aiohttp, etc.) have a distinct TLS fingerprint. In that case, use Playwright or Puppeteer so the fingerprint matches a real browser. See Bypass Cloudflare for Web Scraping and Headless Browser Scraping Guide. Pair with Residential Proxies for best success.

Summary

This HTTP header checker shows request and response headers and, when available, TLS fingerprint (e.g. JA3). Use it to debug why a site blocks your scraper: often the User-Agent or TLS fingerprint gives you away. Fix by setting a realistic User-Agent (see our User-Agent Generator) or switching to a real browser (Playwright). For strict sites, pair with Residential Proxies.

More resources

• User-Agent Generator — get browser-like User-Agent strings.
• Scraping Test — test a URL with your headers and proxy.
• How Bot Detection Systems Work — how sites detect bots.
• Web Scraping Detection Methods — detection overview.
• Preventing Scraper Fingerprinting — reduce fingerprint surface.

Quick tips

• Compare the headers and TLS fingerprint you see here with what a real Chrome session sends (e.g. open the same URL in Chrome and use dev tools or a separate checker). Gaps (missing client hints, wrong JA3) explain why you might be blocked.
• If you use Python requests or Node, set at least User-Agent, Accept, and Accept-Language to match a real browser. Use our User-Agent Generator and Scraping Test to verify the target accepts your requests.
• For Cloudflare and similar, switching to Playwright with Residential Proxies is often the most reliable fix; see Bypass Cloudflare for Web Scraping.

Common header mistakes

• Default library User-Agent — Python requests, Node axios, and curl send identifiable UAs. Replace with a browser UA from our User-Agent Generator.
• Missing Accept or Accept-Language — Real browsers always send these. Add them to match your chosen User-Agent.
• Wrong or missing client hints — Modern Chrome sends Sec-CH-UA and related headers. Only a real browser sends them correctly; scripts often omit or mismatch them, which can contribute to fingerprinting. When in doubt, use Headless Browser Scraping Guide and Residential Proxies.

See also

• Playwright Proxy Configuration Guide — proxy + browser.
• Using Requests for Web Scraping — headers in Python.
• Web Scraping with Node.js — headers in Node.
• Scraping Test — test a URL with your client.

Run this checker from the same environment (same machine or same proxy) you use for scraping so the results match what the target site sees. For production, pair correct headers with Residential Proxies.

If TLS fingerprint (JA3) is shown, compare it to a real Chrome session. Mismatches often explain why scripted requests get challenged even with a browser User-Agent. Fix by using Playwright; see Bypass Cloudflare for Web Scraping. Use our User-Agent Generator for script-based scraping and Residential Proxies for production.

• Compare your scraper’s headers with a real browser using this tool from both environments.
• When moving to Playwright, run the checker again to confirm TLS and headers match Chrome. Then use Residential Proxies for production scraping.
• Bookmark this tool and run it whenever you change client, proxy, or User-Agent to avoid surprises in production. See Bypass Cloudflare for Web Scraping for the full browser + proxy setup.
• Run the checker from the same IP and environment as your scraper for accurate results.

Related reading

• Browser Fingerprinting Explained — what sites detect.
• Bypass Cloudflare for Web Scraping — headers and browsers.
• How Websites Detect Scrapers — detection methods.
• Residential Proxies — pair good headers with clean IPs.

Fighting blocks? Read Browser Fingerprinting Explained and Bypass Cloudflare for Web Scraping. Need proxies? Try our Residential Proxies.