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Edge Case & Unicode Test String Generator

Generate the strings that break input handling — Unicode, RTL, emoji, injection patterns and boundary lengths.

Edge case test strings are the inputs that break naive validation: empty and whitespace-only values, combining diacritics, emoji ZWJ sequences, right-to-left overrides, boundary lengths at 255 and 256 characters, numeric limits, quoting and escaping traps, mixed line endings, and awkward real-world names. Feed them through your input path to find what your code assumes.

Runs in your browser
Categories
Ten — empty values, Unicode, emoji, right-to-left, lengths, numerics, injection, escaping, line endings and awkward names
Safety
Injection entries are inert text for testing your own escaping — nothing here executes
Privacy
Runs entirely in your browser — nothing is uploaded
Cost
Free, unlimited, no sign-up

Frequently asked questions

Are the injection strings dangerous?

No. They are plain text. They only cause a problem if your own code interpolates them into SQL, HTML or a shell command without escaping — which is precisely the bug you are using them to find.

Why do 255 and 256 characters both appear?

Because column limits and buffers are overwhelmingly sized at powers of two. Testing either side of the boundary catches off-by-one truncation that a single 300-character string would hide.

Why does copying from the plain-text output lose some characters?

Zero-width spaces, bidi overrides and null bytes are invisible and are frequently stripped by terminals and text fields. Use the JSON-per-line output, where they appear as escape sequences that survive a copy and paste.

How to use the edge case test string generator

  1. 1Select one or more categories.
  2. 2Choose the output.
  3. 3Turn "Include a description for each" on or off as needed.
  4. 4Set the long-string length.
  5. 5The result appears immediately — copy or download it.

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Put the working edge case test string generator on your own site. It runs in your visitors' browsers exactly as it does here — free, no account, nothing uploaded.

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