Key/value and INI
A simple configuration may contain name=value lines and comments starting with # or ;. INI commonly adds [section] headers. This tool checks that non-comment lines have a key and separator, and reports duplicate keys within a section. Different applications handle quoting, repeated keys and inline comments differently.
Strict JSON
JSON needs double-quoted property names and strings, permits no comments, and rejects trailing commas. This validator uses JSON.parse. Even valid JSON can contain unsupported options; check the schema or application manual separately. Duplicate property names are not diagnosed by JSON.parse.
Other formats
YAML and TOML have many features beyond the basic checks offered here. Shell and Mozilla files may contain executable code. This site never runs configuration code. A successful basic check only means that the few checked conditions passed. Use the official parser or target program for authoritative validation.