Characters that change length on .toUpperCase()

Fuzzer

Created Apr 15, 2024

Updated May 15, 2025

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CategoryJavaScript Syntax

VisibilityPublic

TypeJS

CharsetUTF-8

Template used:

const c = String.fromCodePoint(i);0x0D
0x0D
if (c.length !== c.toUpperCase().length) log(i)

Sample payloads

const c = String.fromCodePoint(i);0x0D
0x0D
if (c.length !== c.toUpperCase().length) alert(i)