parcel-bundler/lightningcss

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An extremely fast CSS parser, transformer, bundler, and minifier written in Rust.

Stars: 7.7k
Forks: 302
Open beginner issues: 0
Indexed issues: 334

Dominant language: Rust
License: MPL-2.0
Last GitHub push: Jul 20, 2026
Latest indexed: Sep 19, 2026
Contributing guide: Contributing guide
Code of conduct: No code of conduct
Beginner labels: good first issue help wanted
PR merge metrics: No merged PRs in 30d

Beginner friendly Everything

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334 open issues indexed

Option to allowlist custom (non-standard) pseudo-classes/elements to suppress "not recognized" warnings Open

Difficulty 4/5 3-5 days Newbie friendliness 52/100

parcel-bundler/lightningcss#1346 · Opened Sep 18, 2026
transform() merges an unrelated rule's selector into another rule via an incorrect :is(...) descendant combinator Open

Difficulty 4/5 3-5 days Newbie friendliness 42/100

parcel-bundler/lightningcss#1345 · Opened Sep 16, 2026
Merges animation-timeline for scroll driven animations into invalid shorthand Open

Difficulty 3/5 1-2 days Newbie friendliness 70/100

parcel-bundler/lightningcss#1342 · 2 reactions · Opened Sep 8, 2026
Compatibility with 32-bit system Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1331 · Opened Sep 7, 2026
`backdrop-filter` is dropped when it precedes a hand-written `-webkit-backdrop-filter` Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

parcel-bundler/lightningcss#1327 · Opened Sep 5, 2026
engines.node says >= 12.0.0 but node/index.js uses ??= (Node 15) — main entry is a SyntaxError on 12/13/14 Open

Difficulty 1/5 Under an hour Newbie friendliness 88/100

parcel-bundler/lightningcss#1326 · Opened Sep 4, 2026
[bug] Syntax error for container query var evaluation Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

parcel-bundler/lightningcss#1325 · Opened Sep 3, 2026
Minifier wraps a selector list in `:is()` when a target lacks `:has()`, which changes the specificity of every other selector in the list Open

Difficulty 3/5 1-2 days Newbie friendliness 70/100

parcel-bundler/lightningcss#1324 · Opened Sep 2, 2026
CLI panics on Browserslist Baseline queries Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

parcel-bundler/lightningcss#1320 · 1 reaction · Opened Sep 1, 2026
Two-value `overflow` shorthand is emitted for targets that don't support it Open

Difficulty 3/5 1-2 days Newbie friendliness 70/100

parcel-bundler/lightningcss#1319 · Opened Sep 1, 2026
Selector silently dropped from a nested selector list when an earlier rule shares a prefix Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

parcel-bundler/lightningcss#1318 · Opened Sep 1, 2026
Percentage math functions panic in percentage-typed contexts Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1312 · Opened Aug 21, 2026
Minifier silently drops a rule when a selector list is split and another selector in that list duplicates an earlier rule Open

Difficulty 4/5 3-5 days Newbie friendliness 55/100

parcel-bundler/lightningcss#1310 · Opened Aug 18, 2026
[bug] v1.33.0 rejects valid ::search-text:current and ::search-text:not(:current) selectors Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

parcel-bundler/lightningcss#1303 · 1 reaction · Opened Aug 5, 2026
[Bug] 'highlight' is not recognized as a valid pseudo-element, even though it is present in `src/selector` Open

Difficulty 2/5 1-3 hours Newbie friendliness 82/100

parcel-bundler/lightningcss#1300 · 3 reactions · Opened Jul 31, 2026
Gamut mapping returns at the first under-JND chroma, producing desaturated sRGB fallbacks Open

Difficulty 3/5 1-2 days Newbie friendliness 74/100

parcel-bundler/lightningcss#1298 · Opened Jul 29, 2026
Unbounded recursion in selector, math-function and rule-nesting parsing overflows the stack Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1297 · Opened Jul 29, 2026
Consider adding an explicit copyright notice to the LICENSE file Open

Difficulty 1/5 Under an hour Newbie friendliness 78/100

parcel-bundler/lightningcss#1296 · Opened Jul 28, 2026
Chaining a pseudo-class after the '::picker' pseudo-element is not allowed. Open

Difficulty 3/5 1-2 days Newbie friendliness 58/100

parcel-bundler/lightningcss#1292 · 4 comments · 2 reactions · Opened Jul 1, 2026
Unexpected behavior when transforming `display: flex` with vendor prefixes Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 55/100

parcel-bundler/lightningcss#1291 · 1 comment · Opened Jun 29, 2026
Unexpected transformation of x units in image-set() Open

Difficulty 3/5 1-2 days Newbie friendliness 65/100

parcel-bundler/lightningcss#1286 · Opened Jun 24, 2026
Error: [lightningcss minify] Cannot find module '../lightningcss.openharmony-arm64.node' Open

pending triage

Difficulty 4/5 3-5 days Newbie friendliness 45/100

parcel-bundler/lightningcss#1285 · Opened Jun 24, 2026
`animation-timeline: view()` added to `animation` shorthand Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

parcel-bundler/lightningcss#1283 · 6 comments · 8 reactions · Opened Jun 23, 2026
Support multiple input files to single output file with CLI Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1280 · 1 reaction · Opened Jun 17, 2026
Simplify division of like units to unitless constant Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

parcel-bundler/lightningcss#1279 · Opened Jun 17, 2026
Support for `<color-interpolation-method>` in gradients Open

parcel-bundler/lightningcss#1272 · 1 assignee · Opened Jun 9, 2026
Make the `mod parser` public. Open

pending triage

Difficulty 2/5 1-3 hours Newbie friendliness 52/100

parcel-bundler/lightningcss#1270 · 2 comments · Opened Jun 5, 2026
Error: [lightningcss minify] Cannot find module '../lightningcss.linux-arm64-musl.node' Open

Difficulty 4/5 3-5 days Newbie friendliness 45/100

parcel-bundler/lightningcss#1269 · 1 reaction · Opened Jun 5, 2026
Add prebuilt riscv64 (linux-gnu) binary Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

parcel-bundler/lightningcss#1267 · 1 reaction · Opened Jun 5, 2026
Incompatible selectors can be dropped after rule merging when targets require selector splitting Open

Difficulty 4/5 3-5 days Newbie friendliness 55/100

parcel-bundler/lightningcss#1260 · Opened Jun 2, 2026
`view-transition-name: match-element` is incorrectly transformed Open

area: css-modules

Difficulty 3/5 1-2 days Newbie friendliness 65/100

parcel-bundler/lightningcss#1256 · Opened May 27, 2026
Support Relative Alpha Colors(CSS Color 5 alpha() function) Open

parcel-bundler/lightningcss#1255 · 1 comment · 1 reaction · 1 assignee · Opened May 27, 2026
Expose current filename to visitors Open

area: custom visitors

Difficulty 3/5 1-2 days Newbie friendliness 55/100

parcel-bundler/lightningcss#1254 · 2 comments · Opened May 27, 2026
Colour precision too high Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 68/100

parcel-bundler/lightningcss#1252 · Opened May 26, 2026
Logical border radius polyfill is hoisted into pseudo classes, breaking base styles Open

area: transpilation

Difficulty 3/5 1-2 days Newbie friendliness 72/100

parcel-bundler/lightningcss#1246 · 1 comment · Opened May 21, 2026
Selecting `::details-content::before` pseudo element errors Open

Difficulty 3/5 1-2 days Newbie friendliness 58/100

parcel-bundler/lightningcss#1244 · 4 comments · 2 reactions · Opened May 19, 2026
Pseudo-element arg inside `:has()` / `:is()` / `:where()` is dropped, leaving an empty `()` and an invalid output selector Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1239 · Opened May 12, 2026
Stale StyleRuleKey hash after merge_style_rules causes missed dedup and nondeterministic minified output Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 74/100

parcel-bundler/lightningcss#1235 · 1 comment · Opened May 4, 2026
Transpile font-width <-> font-stretch Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1234 · Opened May 3, 2026
Make inputSourceMap available via CLI Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

parcel-bundler/lightningcss#1230 · Opened Apr 24, 2026
animation-range keywords (entry/exit) transformed incorrectly during build Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 58/100

parcel-bundler/lightningcss#1226 · 1 comment · Opened Apr 21, 2026
Minification reorders duplicate declarations for `position`, `direction`, and `unicode-bidi` when one uses `var()` Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 68/100

parcel-bundler/lightningcss#1225 · Opened Apr 21, 2026
New color-mix() features: optional interpolation method, variadic color arguments Open

Difficulty 4/5 3-5 days Newbie friendliness 48/100

parcel-bundler/lightningcss#1224 · 1 comment · 2 reactions · Opened Apr 20, 2026
`@layer` ordering declaration is silently dropped when followed by `@layer` blocks Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 72/100

parcel-bundler/lightningcss#1222 · 5 comments · 3 reactions · Opened Apr 19, 2026
`font-family: monospace, monospace` should not deduplicate (the duplication is load-bearing) Open

pending triage

Difficulty 3/5 1-2 days Newbie friendliness 52/100

parcel-bundler/lightningcss#1221 · 6 comments · 2 reactions · Opened Apr 15, 2026
minify: linear-gradient(0deg... with percentages is incorrectly rotated Open

Difficulty 3/5 1-2 days Newbie friendliness 55/100

parcel-bundler/lightningcss#1220 · 1 comment · Opened Apr 15, 2026
Negative scientific notation numbers are emitted incorrectly Open

Difficulty 3/5 1-2 days Newbie friendliness 67/100

parcel-bundler/lightningcss#1219 · 1 comment · Opened Apr 15, 2026
`composes:` silently accepts references to non-existent local classes Open

Difficulty 3/5 1-2 days Newbie friendliness 72/100

parcel-bundler/lightningcss#1215 · Opened Apr 14, 2026
`transition` shorthand incorrectly combines `inherit` with other longhand sub-properties Open

Difficulty 3/5 1-2 days Newbie friendliness 56/100

parcel-bundler/lightningcss#1214 · Opened Apr 13, 2026
`:-webkit-any(:lang(...))` and `:-moz-any(:lang(...))` rules dropped when targets are set Open

pending triage

Difficulty 4/5 3-5 days Newbie friendliness 52/100

parcel-bundler/lightningcss#1211 · Opened Apr 8, 2026

parcel-bundler/lightningcss

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