Suggest an editImprove this articleRefine the answer for “What does a postprocessor do at build time?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**A postprocessor at build time** takes CSS code that already exists (written by hand or generated by a preprocessor) and automatically modifies it before it ships to production. **Key point:** it performs one or several tasks depending on which plugins are connected, making the CSS cross-browser, compact, logical and fast to load.Shown above the full answer for quick recall.Answer (EN)ImageA postprocessor at build time takes CSS code that already exists (written by hand or generated by a preprocessor) and **automatically modifies it before it ships to production**. Specifically, it performs one or several tasks depending on which plugins are connected. --- ### **What exactly a postprocessor does at build time** **1. Adds cross-browser prefixes** To make CSS work correctly in older browsers, it adds `-webkit-`, `-moz-`, `-o-` wherever caniuse data says they are needed. **2. Optimizes and cleans up CSS** - shortens property notation - removes unused code (if PurgeCSS is connected) - groups repeating rules **3. Minifies the final file** - removes whitespace and line breaks - compresses the CSS - reduces the overall size for faster loading **4. Converts modern CSS into something older browsers understand** For example, it lets you use future specifications (via `postcss-preset-env`), turning them into compatible code. **5. Automates routine tasks** Depending on the plugins: sorting properties, merging media queries, generating fallback values and so on. --- ### **Final purpose** A postprocessor makes CSS **ready for production**: it makes the code **cross-browser, compact, logical and fast** to load. Put in one line: > **A preprocessor makes writing CSS simpler, while a postprocessor brings it to an ideal state before publishing.** Shall we continue?For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.