Regex Invalid Flag Error – Fix Unsupported JavaScript Flags

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Replace an unsupported regular-expression flag before JavaScript tries to compile the pattern.

3 chars · 1 line

8 chars · 1 line

Pattern did not match the inputFlags: g

Regex flag error

How to fix an unsupported JavaScript regex flag

Regex flavors do not share one universal flag set. This JavaScript tester accepts d, g, i, m, s, u, v, and y; an unrelated flag such as q is rejected before the pattern runs. This tool is free to use. No account or payment is required.

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What you can do here

  • JavaScript RegExp validation
  • Broken pattern preloaded
  • Corrected pattern comparison
  • Configurable regex flags
  • Browser-native error feedback
  • Browser-local processing

Steps

  1. Identify the unsupported letter in the flags field.
  2. Check what behavior that flag represented in the source regex flavor.
  3. Remove it or translate the behavior to supported JavaScript syntax before testing again.

Regex flags are flavor-specific

A pattern copied from PCRE, Python, .NET, an editor, or another tool may include mode syntax that JavaScript expresses differently. Validate the flags separately from the pattern when porting a regex.

Unsupported regex flag example

Remove q when the pattern does not require a JavaScript equivalent.

Invalid flags

q

Corrected flags

Common questions

Frequently asked questions

Which flags does this Regex tool accept?

It accepts d, g, i, m, s, u, v, and y and rejects duplicates.

Why does a regex copied from another language fail?

Different regex flavors support different flags and syntax. Translate flavor-specific options before compiling with JavaScript RegExp.

Is an empty flags field valid?

Yes. A JavaScript regex can compile with no flags.

Recommended next steps

Regex Duplicate FlagRemove repeated JavaScript regex flags such as gg or ii.Regex Trailing BackslashRemove or complete an escape sequence that ends with a lone backslash.Regex Tester Online – Test JavaScript PatternsCompile a JavaScript pattern and flags locally against sample text.

Debugging a specific Regex issue? Browse Regex troubleshooting.