When reviewing website logs, firewall activity, or traffic statistics, you may notice requests originating from automated crawlers, also known as bots or spiders.
These bots are commonly used by search engines and online platforms to:
- Index website content.
- Generate search engine results.
- Create social media link previews.
- Analyze website structure.
- Collect publicly available information.
Each crawler identifies itself using a User-Agent string, which can help you determine whether unusual traffic originates from a legitimate service or a potentially malicious bot.
Table of Contents
Why Is This Information Useful?
Knowing common User-Agent names can help you:
- Analyze traffic spikes.
- Identify search engine crawlers.
- Verify indexing activity.
- Create firewall or security rules.
- Troubleshoot website performance.
- Detect suspicious activity masquerading as a search engine bot.
How to Check User-Agent Information
User-Agent information can typically be found in:
- Web server logs
- Access logs
- Analytics platforms
- Security tools
- Firewall reports
When investigating crawler activity, look for the User-Agent field in the request details.
Popular Search Engine Crawlers
Google – Googlebot
Short Name
Googlebot
Example User-Agent
Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
Microsoft Bing – Bingbot
Short Name
Bingbot
Example User-Agent
Mozilla/5.0 (compatible; Bingbot/2.0; +http://www.bing.com/bingbot.htm)
Yahoo – Slurp
Short Name
Slurp
Example User-Agent
Mozilla/5.0 (compatible; Yahoo! Slurp; http://help.yahoo.com/help/us/ysearch/slurp)
DuckDuckGo – DuckDuckBot
Short Name
DuckDuckBot
Example User-Agent
DuckDuckBot/1.0; (+http://duckduckgo.com/duckduckbot.html)
Baidu – Baiduspider
Short Name
Baiduspider
Example User-Agent
Mozilla/5.0 (compatible; Baiduspider/2.0; +http://www.baidu.com/search/spider.html)
Yandex – YandexBot
Short Name
YandexBot
Example User-Agent
Mozilla/5.0 (compatible; YandexBot/3.0; +http://yandex.com/bots)
Other Popular Crawlers
Sogou Spider
Common User-Agent examples:
Sogou Pic Spider/3.0
Sogou head spider/3.0
Sogou web spider/4.0
Sogou Orion spider/3.0
Sogou-Test-Spider/4.0
ExaLead – Exabot
Short Name
Exabot
Example User-Agents
Mozilla/5.0 (compatible; Exabot/3.0; +http://www.exabot.com/go/robot)
Mozilla/5.0 (compatible; Konqueror/3.5; Linux) KHTML/3.5.5 (like Gecko) (Exabot-Thumbnails)
Social Media Crawlers
Facebook Link Preview Bot
When a link is shared on Facebook, Meta uses a crawler to retrieve page information and generate a preview.
Short Name
facebookexternalhit
Example User-Agents
facebookexternalhit/1.0
facebookexternalhit/1.1
Analytics and Ranking Crawlers
Alexa Crawler
Short Name
ia_archiver
Example User-Agent
ia_archiver (+http://www.alexa.com/site/help/webmasters; [email protected])
Verifying a Suspected Googlebot
Not every bot that claims to be Googlebot is legitimate.
Some malicious crawlers intentionally spoof Googlebot User-Agent strings.
If you need to verify whether a request actually originated from Google, Google provides documentation on validating crawler IP addresses.
You can also use:
Google Search Central – Verify Googlebot
Blocking or Allowing Crawlers
If necessary, crawler access can be managed through:
robots.txt
Example:
User-agent: Googlebot
Disallow:
.htaccess
Example:
RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} BadBot [NC]
RewriteRule .* - [F,L]
Note: Blocking legitimate search engine crawlers may negatively affect your website’s visibility in search results.
Important Security Note
Not all bots visiting your website are beneficial.
While search engine crawlers help index your content, some automated bots may:
- Search for vulnerabilities.
- Attempt brute-force attacks.
- Scrape website content.
- Probe outdated software.
To reduce risk:
- Keep your CMS updated.
- Update plugins and themes regularly.
- Monitor access logs.
- Use security plugins and firewalls.
- Block known malicious bots when appropriate.
Summary
User-Agent strings allow you to identify the source of automated traffic.
Some of the most common crawler names include:
| Service | User-Agent |
|---|---|
| Googlebot | |
| Bing | Bingbot |
| Yahoo | Slurp |
| DuckDuckGo | DuckDuckBot |
| Baidu | Baiduspider |
| Yandex | YandexBot |
| facebookexternalhit | |
| Alexa | ia_archiver |
| ExaLead | Exabot |
Understanding these identifiers can help you analyze traffic patterns, troubleshoot indexing issues, and distinguish legitimate crawlers from potentially malicious bots.