Verdict
Violentmonkey is a practical choice for users who prefer open-source userscript tooling and a familiar lightweight workflow. ScriptCat is a practical choice for users who want to test alternative userscript manager behavior or explore a different development community. Neither is universally better — the right choice depends on your existing script library, browser version, and workflow preferences. Test important scripts before committing to either option.
Key Differences
- Violentmonkey has a longer track record and a well-established open-source community; ScriptCat is a more recently active project.
- Both support the standard userscript API, but script compatibility may vary depending on specific @grant and @match rules.
- Violentmonkey is widely available in the Chrome Web Store as an MV3 extension; ScriptCat availability varies across browser versions.
- Both require users to review script permissions — the specific @match domains and GM_* API usage matters more than the manager brand.
- Migration effort between them is moderate — scripts are generally compatible, but testing each script individually is recommended.
Side-by-side Comparison
| Option | Best For | MV3 | Cost | Open Source | Setup | Main Trade-off |
|---|---|---|---|---|---|---|
| Violentmonkey | Users who prefer open-source userscript tooling and a familiar lightweight workflow | Available (MV3) | Free / Open source | Fully open source | Easy | Minimal interface, smaller community than Tampermonkey |
| ScriptCat | Users testing alternative userscript manager workflows or advanced script behavior | Available (MV3) | Free | Open source | Easy | Different community and update cadence than Violentmonkey |
| Tampermonkey (related) | Users who need the widest script library and most established ecosystem | Available (MV3) | Free / Donationware | Partial | Easy | Larger resource usage but more built-in features |
Which One Should You Choose
You prefer open-source userscript tooling, a lightweight interface, and a familiar workflow.
You are testing alternative userscript manager behavior or want to explore a different script workflow community.
You need broad userscript compatibility, the largest established ecosystem, and a familiar interface.
Avoid unknown scripts
You encounter scripts from random mirrors or sources you cannot verify. Script trust matters more than the manager brand.
Common Failed Fixes
Trying to: Import every script at once without reviewing @match and @grant rules
Why it does not work: Scripts may request permissions or access domains that behave differently under a different manager. Each script may need individual review.
Safer alternative: Import and test scripts one at a time on non-sensitive pages before enabling them site-wide.
Trying to: Assume Violentmonkey and ScriptCat behave identically for all scripts
Why it does not work: Both support the standard userscript API but implementation details and permission handling may differ. Some scripts with advanced GM_* calls may not work the same way.
Safer alternative: Check the specific script documentation and test on a non-sensitive page after switching managers.
Trying to: Ignore @match and @grant permissions in scripts
Why it does not work: Permissions define what a script can access. Reviewing them is the most important safety step regardless of which manager you use.
Safer alternative: Read the @match domains and @grant rules in each script before installing, especially for scripts from third-party sources.
Trying to: Install scripts from unknown mirrors or third-party download sites
Why it does not work: Scripts bundled with unwanted code from unofficial sources can read page content and track browsing. Use the official userscript registry or the developer's own site.
Safer alternative: Install scripts from the original developer or known userscript library. Verify the source before installing.
Trying to: Keep multiple managers enabled with overlapping scripts
Why it does not work: Running Violentmonkey, ScriptCat, and Tampermonkey at the same time can cause scripts to run twice, create conflicts, or behave unexpectedly.
Safer alternative: Choose one primary manager and import scripts carefully into that one.
Frequently Asked Questions
Sources
- Violentmonkey Official SiteViolentmonkeyPrimary source
Supports: Official Violentmonkey site and download information
- Violentmonkey GitHub RepositoryViolentmonkeyPrimary source
Supports: Official source for Violentmonkey development and MV3 status
- ScriptCat GitHub RepositoryScriptCatPrimary source
Supports: Official source for ScriptCat development and availability
- Chrome Extension Permissions OverviewGoogle Chrome DevelopersSecondary source
Supports: Understanding userscript permission implications