Quick Answer
Violentmonkey and ScriptCat are both userscript manager options, but they may fit different users depending on browser support, script compatibility, permissions, and workflow preferences. Violentmonkey is commonly chosen by users who prefer open-source userscript tooling and a familiar lightweight workflow. ScriptCat may appeal to users testing alternative userscript manager behavior or more advanced script workflows. Neither option makes unknown scripts safe by default. Users should review script sources, inspect @match and @grant rules, and test important scripts on non-sensitive pages before switching managers.
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