Browser Compatibility Query

Query browser compatibility data for web features using the caniuse CLI tool.

Prerequisites Check

Before querying, verify caniuse-cli is installed:

which caniuse || echo "NOT_INSTALLED"

If not installed, tell the user:

caniuse-cli is not installed. Install it with:

npm install -g @bramus/caniuse-cli

Querying Compatibility

Run the caniuse command with the feature name:

caniuse <feature-name>

Feature name formats:

• Hyphenated: caniuse viewport-units
• Quoted phrases: caniuse "viewport units"
• With special chars: caniuse @property

Common feature name mappings (user term → caniuse query):

• :has() selector → css-has
• :where() selector → css-where
• :is() selector → css-matches-pseudo
• container queries → css-container-queries (size) or css-container-queries-style (style)
• CSS nesting → css-nesting
• subgrid → subgrid
• aspect-ratio → css-aspect-ratio
• gap in flexbox → flexbox-gap
• CSS grid → css-grid
• flexbox → flexbox

JS/API features:

• ES modules → es6-module
• async/await → async-functions
• optional chaining → mdn-javascript_operators_optional_chaining
• fetch API → fetch
• service workers → serviceworkers
• WebGPU → webgpu

Presenting Results

After running the command:

1. Show the compatibility table as returned by caniuse

2. Highlight key findings:

   • Which major browsers fully support it
   • Any browsers with partial support (note the limitations)
   • Browsers that don't support it at all

3. Call out important notes if the output includes numbered notes (these often contain critical info about prefixes, flags, or partial implementations)

4. Give practical advice based on the results:

   • If widely supported: "Safe to use in production"
   • If partial support: "Works but check the notes for limitations"
   • If poor support: "Consider a polyfill or fallback"

Handling Unknown Features

If caniuse returns "Nothing was found":

1. Check the mapping table above — many features have specific caniuse names (e.g., :has() → css-has)

2. Try common prefixes:

   • CSS properties: try css- prefix (e.g., css-grid, css-variables)
   • MDN data: try mdn- prefix for JS features

3. Try variations:

   • Remove special characters: :has() → has or css-has
   • Use hyphens: "container queries" → container-queries

4. If still not found, tell the user:

   This feature might not be in the caniuse database, or uses a different name. Check https://caniuse.com to find the correct feature name.