INI Duplicate Key Error Example
Check INI text for sections, key=value lines, comments, and duplicate names. It does not look for HTML tags.
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Result
About this tool
This page opens the INI validator preloaded with a short application settings file that contains a real, common mistake: the debug key is set to false and then, two lines later, set again to true inside the very same [application] section — most likely a leftover line from testing that was never removed. The failing check below runs live the moment the page loads and reports the exact line of the second, conflicting assignment.
INI parsers disagree on what to do with a repeated key in one section — some silently keep the first value, some keep the last, and some throw an error — which is exactly why this is a dangerous mistake rather than a harmless one: the same file can behave differently depending on which tool reads it. Catching the duplicate before it ships removes that ambiguity entirely.
Replace the sample with your own INI file to see the same per-section duplicate-key check applied to it. Compare it against the ini-config-example preset to see the same section structure with every key appearing exactly once and passing cleanly.
Example. [app]\nname = demo passes. A second [app] fails with Duplicate INI section found. Inside one section, debug = 0 followed by debug = 1 fails on the second line with Duplicate key "debug".
Limit. Comments are only whole lines that start with # or ;. Values are not typed, continuations are not joined, and the checker does not look for HTML tags.