Compile LESS to CSS Online — less.js Browser Compiler
Compile one LESS snippet or bundle a local project folder with native @import resolution. Compress output and use source maps for single files — everything runs in your browser.
Developer notes
• Drop a project folder to resolve local @import paths. node_modules, packages and remote URLs are not resolved. • Inline JavaScript in LESS is off by default; enable only if you trust the source. • Strict math requires parentheses around calculations when enabled. • Auto-compile on paste/sample; typed edits need Compile (⌘↵). • Source maps are available for single files and unavailable in bundle mode v1.
Bundle local partials
Choose Bundle project, drop a folder, then select one entry file. FastMinify preserves relative paths and lets Less discover reachable .less files through @import. The browser-local bundle is limited to 32 MiB per file and 32 MiB total. Version 1 has one entry, no source maps and no node_modules package resolution.
Options
When teams pick this route
• Convert legacy LESS components to CSS for migration. • Preview parametric mixins before integrating into a build. • Share compiled CSS with teammates who do not use LESS. • Quick-check guard expressions and operations.
Worked examples
Variables and operations
LESS input
Compiled CSS
Parametric mixin
LESS input
Compiled CSS
Navigate related tools
Beautify LESS with beautify LESS, decompress with unminify LESS, or browse the CSS preprocessors hub.
LESS compiler FAQ
Browser-only compilation
Why can't I use @import for Bootstrap or other libraries?
Project bundles resolve local .less files that you drop into the browser. Paths to node_modules, packages, CDNs or files outside that dropped folder are not available.
What does Strict math do?
When enabled, calculations like 8px + 4px require parentheses. This matches stricter LESS compiler modes used in some build pipelines.
When does compilation run automatically?
On paste and sample load. Typing alone does not trigger compilation — use Compile or ⌘↵.
Is a project bundle the same as concatenating files?
No. Less starts from one entry file and resolves only the @import dependencies it reaches. File order is not manually concatenated. Bundle mode v1 is limited to one entry, 32 MiB total, no source maps and no npm package imports.
CSS preprocessors
Compile SCSS or LESS to standard CSS in the browser — pair with beautify or minify for a full stylesheet workflow.
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Expand minified or compressed code — unminify JavaScript, CSS, TypeScript, SCSS, LESS, SQL, YAML and other formats when debugging or reviewing.
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Transform data between JSON, YAML, XML and CSV locally — no server uploads.
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Encode or decode Base64, URL components and HTML entities — client-side only.
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Paste-local WCAG contrast checking with modern CSS color syntax — pair and matrix views, never uploaded.
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Terraform HCL format/validate/minify, Dockerfile format & lint, Docker Compose and .env validation.
CI/CD
GitHub Actions and GitLab CI — format YAML and check workflow/job structure in your browser.
Logs & observability
Line-oriented JSON/NDJSON and Nginx/Apache access logs — format, filter, validate, and CSV/TSV.
Kubernetes
Multi-doc manifests, structural validate, Ingress/Deployment starters, and Helm values formatting.
Networking / IP
CIDR, subnets, and IPv4/IPv6 helpers — in your browser.
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JWKS, X.509 certificates, and secrets scan — browser-local.
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OpenAPI tools to format, validate, and lint your specs.
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Paste-local cURL, HTTP messages, URLs, HAR files, and Cookie / Set-Cookie headers — format and inspect in your browser, never sent.
Developer utilities
Timestamps, UUID, ULID, Nanoid, cron, passwords, regex, slugify, number bases, case, text diff, and chmod — all client-side.
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Count words, build Markdown TOCs, and clean line lists — all in your browser.
AI & LLM
Token counting, pricing estimates, and context-window fit — 100% browser-local.
Test Data
Synthetic field values for fixtures and DB seed — reserved-range phone numbers first.