Common developer fixes

JSON does not allow trailing commas after the final object property or array item. Remove the last comma, then format or validate again.

Unexpected token errors usually mean invalid quotes, comments, missing commas, or extra text before or after the JSON value.

YAML uses indentation to define structure. Mixing levels, tabs, or misaligned list items can change the document or make it fail.

A mismatched tag means an opening element was closed with the wrong name or nesting order.

Base64 decoding fails when the string includes unsupported characters, whitespace in the wrong place, URL-safe variants, or missing padding.

A JWT should usually contain three dot-separated segments: header, payload, and signature. Decode errors often come from missing segments or malformed Base64URL text.

Invalid group errors usually come from unsupported group syntax, missing parentheses, or lookbehind patterns in environments that do not support them.

A missing brace can cause later selectors to be parsed inside the wrong rule. Add the missing closing brace, then format CSS to confirm structure.