What is the cURL User-Agent string?

The cURL User-Agent string is: curl/8.5.0

Does cURL respect robots.txt?

No, cURL does not reliably respect robots.txt. Additional measures like IP blocking may be needed.

CURL

Q: How do I block cURL in robots.txt?

To control cURL access, add the following to your robots.txt file: # cURL does not check robots.txt. # Detection via User-Agent 'curl/' is trivial but easily bypassed. # Focus on behavioral and TLS fingerprint detection.

MEDIUM RISK📊 SEO & DATA SCRAPER

Command-line HTTP client — the most ubiquitous tool for automated HTTP requests

ORGANIZATION

Open Source

FIRST SEEN

1998-01

RESPECTS ROBOTS.TXT

✗ NO

DOCUMENTATION

curl.se

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DAILY VISITS

—

COUNTRIES ACTIVE

TRACKING

STATUS

—

LAST SEEN

📡 CURL USER-AGENT STRING

curl/8.5.0

This is the User-Agent header sent by cURL in HTTP requests. Use this to identify cURL in your server access logs.

📋 ABOUT CURL

cURL is the world's most widely-used command-line tool for transferring data via URLs, installed by default on virtually every Linux, macOS, and modern Windows system. Created by Daniel Stenberg in 1998, cURL supports dozens of protocols and is used billions of times daily for API testing, health monitoring, automated downloads, and scripting.

cURL's default User-Agent string 'curl/X.X.X' is commonly seen in web server logs and typically indicates automated or scripted access. While changing the User-Agent is trivial (-A flag), cURL's TLS fingerprint and connection characteristics remain distinctive and can be identified by advanced detection systems like NORAD.

NORAD.io tracks cURL-based access as a medium-risk signal. While cURL itself is a neutral tool with many legitimate uses, its presence in web traffic logs (especially with the default User-Agent) often indicates automated access. NORAD's TLS fingerprinting technology (JA3/JA4) can identify cURL connections even when the User-Agent is spoofed to mimic a standard browser.

🎯 HOW TO DETECT CURL

▸Default User-Agent is 'curl/X.X.X' — trivially changed with -A flag
▸Missing browser headers: no Accept-Language, no Sec-Fetch-* headers
▸TLS fingerprint is distinctive (different cipher suites than browsers)
▸Single-request pattern — no session cookies, no referrer chains
▸Often used from servers and CI/CD pipelines

🔄 CRAWL BEHAVIOR

Single-request tool with no built-in crawling, spidering, or rate limiting. Each invocation fetches one URL. Behavior is entirely determined by command-line arguments. Does not render JavaScript.

PURPOSE

General-purpose HTTP client used for API testing, health checks, debugging, automated downloads, and scripting. Present on virtually every Unix/Linux system.

🤖 ROBOTS.TXT CONFIGURATION

# cURL does not check robots.txt.
# Detection via User-Agent 'curl/' is trivial but easily bypassed.
# Focus on behavioral and TLS fingerprint detection.

⚠ cURL may not fully respect robots.txt. Consider supplementing with IP-level blocking or bot detection middleware.

→ Complete Guide: robots.txt for AI Bots