YouTube comments refuse to paste in Firefox, but Ctrl+C still works. The cause is a hidden preference called dom.event.clipboardevents.enabled that blocks paste events. Flipping it back to true in about:config restores the comment box in seconds.
If the preference is already on, an extension or corrupted YouTube cookies are usually to blame. Try a Private Window test, then update Firefox or clear site data to fully resolve it.
In this guide, I have covered:
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Why can’t I copy and paste on YouTube in Firefox?
YouTube’s comment box relies on JavaScript to handle paste events. Firefox ships with a hidden preference called dom.event.clipboardevents.enabled that controls whether websites can listen for those events. When that preference is set to false, the comment editor refuses to accept anything you paste, even though the operating system clipboard still works fine elsewhere.
You can usually copy text out of YouTube with Ctrl+C just fine, but the moment you press Ctrl+V inside a comment field, nothing appears. Right-click paste, the menu bar paste option, and even drag-and-drop text all fail the same way. Other sites with rich text editors can show the exact same symptom.
Two other common culprits ride along with the same behavior: an extension that hooks into the clipboard, and an outdated Firefox build. The steps below cover all three, starting with the fix that solves the issue for most readers.
Enable clipboard events in about:config
This is the fix that resolves the issue for most readers. It restores Firefox’s default behavior of letting websites detect paste events.
Click the hamburger menu in the top-right corner of Firefox and choose Settings (called Preferences on macOS). In the address bar, type about:config and press Enter.
Firefox shows a Proceed with Caution page. Click the button labeled Accept the Risk and Continue to open the hidden preferences editor.
In the search box at the top of the page, paste dom.event.clipboardevents.enabled. Look at the row that appears below it. If the value on the right reads false, click the toggle button on the far right of that row to flip it back to true.
Close the about:config tab, return to YouTube, click into a comment field, and try Ctrl+V again. For background on what this preference does, see Mozilla’s Configuration Editor for Firefox support page.
If you used a privacy hardening guide or a user.js file in the past, that script may set this preference back to false on every Firefox start. Re-check about:config after restarting Firefox once to confirm the value stuck.
Disable extensions that block paste events
Some Firefox extensions intercept clipboard events before YouTube’s code can read them. Confirmed offenders in the wild include Swift Selection Search and LanguageTool’s AI grammar checker, but any privacy, form-filler, or grammar extension can be the cause.
Open the hamburger menu 
and choose Add-ons and themes, then click Extensions in the left column. Toggle each extension off one at a time, returning to YouTube to test paste after every change.
When paste works again, the last extension you disabled is the culprit. Leave it off, or open its settings to look for an option to allow paste on YouTube.
TIP: Use a Private Window (Ctrl+Shift+P) as a quick sanity check. Private Windows load YouTube with all extensions temporarily disabled, so if paste works there but not in your normal window, an extension is the cause.
Update Firefox to the latest version
Mozilla ships clipboard and editor fixes in almost every Firefox release. You do not want to chase a bug that was fixed three versions ago.
- Open the Firefox browser app on your computer.
- Click on the More menu and select the Settings menu.
- Scroll down to the Firefox Updates section within the General tab, and click the button.
- Firefox will check for updates and download them. It may ask to restart to complete the installation of the update.
The browser will be updated to the latest version.
After Firefox finishes updating and relaunches, reload YouTube and try pasting into a comment field again. If you skipped updates for a while, you may also want to review our full guide to downloading and updating Firefox.
Clear cookies and site data for YouTube
Corrupted YouTube session data can break the comment editor even when the clipboard preference is set correctly. Wiping YouTube’s stored cookies forces a fresh session and removes any stuck state.
- Open the Firefox browser on your computer.
- Click on the More menu and select the Settings menu.
- Switch to the Privacy & Security tab and scroll to the Cookies and Site data section.
- Click on the button.
- Enable the checkbox for the 'Cookies and Site Data' and 'Cached Web Content' options.
- Hit on the option.
It will immediately delete the cache, cookies, and site data on the browser.
Sign back into YouTube, open any video, and paste into a comment to confirm the fix. If you would rather wipe data without touching other sites, our complete Firefox cookies and cache guide walks through the per-site path.
Reset clipboard permissions for the YouTube site
If the clipboard preference is already on and extensions are off, Firefox may still be holding a stuck permission for the YouTube domain. The site info panel lets you revoke and re-grant it.
Open a YouTube tab and click the lock or shield icon in the address bar. Look for any permission labeled Access your clipboard or similar. If you see one, set it to Block, reload the page, then come back and set it to Allow. This often clears a stuck permission state.
You’ll know it worked when the lock or shield icon disappears, then reappears after reload. You can read more about Firefox’s per-site permission controls in our guide to viewing site info and settings in Firefox.
Quick checklist before you go
Run through this short list in order, and paste on YouTube usually comes back:
- Set dom.event.clipboardevents.enabled to true in about:config.
- Test in a Private Window to rule out extensions.
- Update Firefox to the latest stable build.
- Clear cookies and site data for youtube.com.
- Reload the page and try pasting again.
Frequently Asked Questions
Why can I copy text out of YouTube but not paste into comments on Firefox?
Copy and paste are handled by separate code paths. The dom.event.clipboardevents.enabled preference blocks websites from detecting paste (and cut) events but leaves the copy event alone. That is why text leaves YouTube just fine while paste silently fails inside the comment box.
Does this fix also work for YouTube Studio, Shorts, or community posts?
Yes. YouTube Studio description fields, Shorts captions, and community post text boxes all rely on the same JavaScript paste events. Restoring dom.event.clipboardevents.enabled to true fixes paste in every YouTube text editor that runs in Firefox.
Will enabling clipboard events make Firefox less private?
Setting dom.event.clipboardevents.enabled back to true restores Firefox’s default behavior. Sites can detect that you pressed paste, but they still cannot read your clipboard contents without a separate permission prompt, the same way they could before the preference was changed.
Does this happen on Firefox for Android or iPhone?
The desktop about:config fix targets Firefox on Windows, macOS, and Linux. On Firefox for Android or iPhone, paste failures on YouTube usually come from an outdated app version or a phone-wide clipboard permission, so start by updating Firefox from the Play Store or App Store. For a deeper mobile cleanup, our Firefox history and data clearing guide covers both desktop and mobile.
