What Is a Clipboard Test?
This tool actually writes a real, uniquely-generated test string to your system clipboard using the Clipboard API, then asks you to manually paste it back to confirm the value survived the round trip exactly. The copy step is a genuine API call - not a simulation - and the paste verification requires your own manual paste action, since browsers intentionally don't allow a webpage to silently read your clipboard without your direct involvement.
How to Use the Clipboard Test
- Click "Copy Test Value" - this writes a real random string to your clipboard.
- Click into the text box below it.
- Paste using Ctrl+V (Windows/Linux) or Cmd+V (Mac).
- Check "Paste Verified" - it confirms whether the pasted value exactly matches what was copied.
How It Works
Clicking "Copy Test Value" calls navigator.clipboard.writeText() with a freshly generated
unique string, a genuine write to your operating system's actual clipboard. This tool deliberately does not
attempt to programmatically read the clipboard back - modern browsers require an explicit user action, like
a real paste keystroke, before a page can access clipboard content, as an important privacy and security
protection against silent clipboard snooping. Instead, this test asks you to paste manually into a text
field, then compares what actually appears there against the known test value.
Understanding Your Results
- "Success (verified)" and "Confirmed match" - both copy and paste are working correctly; your clipboard round trip functions as expected.
- Write succeeds but paste shows a different value - something else may have overwritten your clipboard between the copy and paste steps, such as another application or a second copy action; try the test again without copying anything else in between.
- "API not available" - your browser or current context (such as a non-secure HTTP page) doesn't support the Clipboard API; it generally requires a secure HTTPS connection.
- Write fails with "permission denied" - check your browser's site-specific clipboard permission setting, which some browsers require explicit approval for.
Browser Limitations
The Clipboard API's write function generally requires a secure context (HTTPS) and, in most browsers, a direct user gesture like a button click - which this test deliberately relies on rather than trying to copy automatically on page load. Reading the clipboard programmatically is even more restricted across browsers specifically to prevent malicious pages from silently harvesting clipboard content, which is exactly why this test asks you to paste manually rather than attempting an automatic read.
Common Mistakes to Avoid
- Copying something else between the test steps - this will overwrite the test value on your clipboard before you paste it back; run the copy step again immediately before pasting.
- Testing on a non-HTTPS page - the Clipboard API typically requires a secure context to function at all.
- Assuming a failed write always means a browser bug - check for a browser permission prompt that may have been missed or previously denied for this site.
Frequently Asked Questions
Why do I have to paste manually instead of the tool reading it automatically?
Browsers intentionally restrict programmatic clipboard reads to require an explicit user action like a real paste, protecting you from pages silently accessing whatever you've copied.
Does this test send my clipboard content anywhere?
No, everything happens locally in your browser - the test value is only compared within the page and is never transmitted anywhere.
Why does the Clipboard API require HTTPS?
Clipboard access is a sensitive capability, so browsers restrict it to secure contexts as a security measure, preventing clipboard manipulation over insecure, potentially intercepted connections.
What if my paste shows a completely different, unrelated value?
This usually means something else was copied to your clipboard after this test's copy step but before you pasted - simply click "Copy Test Value" again immediately before pasting to retest.
Can I use this to test copying images or files?
No, this test specifically checks text clipboard support through writeText(); image and
file clipboard access use separate, more restricted browser APIs not covered by this test.
Conclusion
A genuine copy-and-paste round trip confirms your clipboard is functioning correctly for real use, not just that the API exists. For a similar functional check of browser storage, see the Web Storage Test.