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Bypassing Cache by User Agent

2 min read

Sometimes you want certain tools to always get a freshly built page, never a cached one. The Bypass User Agents setting lets you do that by matching the visitor’s browser identification string.

What this does

Every request includes a User-Agent string that identifies the browser or tool making it. When you add a value to Bypass User Agents, any request whose User-Agent contains that text skips the cache and gets a freshly built page.

This is useful for tools that should always see the live page, such as:

  • Screenshot bots
  • Internal previews
  • Monitoring services

Settings explained

SettingWhat it doesDefault
Bypass User AgentsRequests from matching User-Agents skip the cacheEmpty

By default this list is empty, so no User-Agents are bypassed. You add only the ones you want.

Matching is a substring check. A value matches if it appears anywhere in the visitor’s User-Agent string. Glob patterns (*, ?, [ ]) and raw regex (with a ~ prefix) are also supported, the same as the other exclusion settings.

Tip: Substring matching is usually all you need here. User-Agent strings vary a lot, so a short, distinctive piece of text is the most reliable thing to match.

How to set it up

  1. Open the xSpeed Cache Cache page in your WordPress admin.
  2. Find the Bypass User Agents setting.
  3. Add one value per line. Each value is a piece of text to look for in the User-Agent.
  4. Save your settings. Saving purges the cache so the rule applies.

Best practices

  • Add only the tools you actually need to bypass. Keeping the list short avoids accidentally bypassing real visitors.
  • Use a distinctive substring from the tool’s User-Agent rather than the whole string.
  • This is for tools, not for regular visitors. Bypassing common browsers would defeat the purpose of caching.

Troubleshooting

  • A monitoring tool reports the wrong page. Add a distinctive piece of its User-Agent string to Bypass User Agents so it always gets a freshly built page.
  • My cache hit rate dropped. Check that a bypass value is not matching ordinary visitors. Make the value more specific.

FAQ

Is the match case-sensitive? No. The substring check ignores case.

Can I use patterns instead of plain text? Yes. Glob patterns and ~ raw regex are supported, but a plain substring is usually the simplest choice.

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