CSS formatter
Lay out bounded CSS rules and declarations locally without applying the stylesheet.
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Code tools tools
Format, validate, and test code without running it.
HTML formatter
Indent bounded static HTML locally without rendering it or executing scripts.
JavaScript formatter
Lay out basic JavaScript structure while keeping pasted code as inert text in your browser.
package.json validator
Check practical package manifest fields locally without resolving, installing, or auditing dependencies.
Regex explainer
Read common regular-expression tokens as plain language and export a compact explanation without running a pattern.
Regex replace tester
Preview a bounded regular-expression replacement locally and export its exact text output.
Regex tester
Test a bounded regular expression against local text, inspect match offsets and captures, then export the report.
SemVer range tester
Test a complete SemVer version against a documented local range subset and export the decision.
CSS, HTML, and JavaScript formatters lay out code as inert text. The package.json validator checks manifest fields, the regex tools explain, test, and preview patterns, and the SemVer tester checks version ranges against a documented subset.
Nothing you paste is executed, no registry is contacted, and no package is installed.
Formatting, validation, and patterns
The CSS, HTML, and JavaScript formatters make minified or messy snippets readable for review, without running them. They are meant for quick inspection of code copied from a site, an email template, or a log. For a codebase, keep using the formatter your team runs in CI. The package.json validator catches the manifest mistakes that break installs and module loading, such as an invalid version or a wrong "type" value.
Regular expressions get three tools: the explainer describes a pattern token by token, the tester shows every match with its offsets and capture groups, and the replace tester previews a substitution before you run it across files. The SemVer range tester answers whether a version satisfies a range like ^1.2.3 or ~2.0.0.
Why nothing is executed
Code from unknown sources can be malicious. A formatted script is still a script, and running it in a browser console to see what it does is how many account takeovers start. These tools treat all input as text: markup is never rendered, scripts are never run, and regular expressions are checked for patterns that could freeze the page before they are tested.
That design also means limits: the formatters are structural rather than full parsers, and the regex tools refuse constructs such as backreferences and nested quantifiers. When a tool cannot handle something faithfully, it says so rather than producing something plausible but wrong.