Unicode Security Inspector — Free Online Tool

Detect invisible Unicode characters, bidi controls, mixed scripts, and common confusable characters locally before sharing text or code.

Use this free online Unicode Security Inspector directly in your browser. No signup required, no data leaves your device. Part of Utilier — a collection of 133+ developer utilities.

What is Unicode Security Inspector?

Unicode lets text represent the world's writing systems, but visually similar characters and invisible format controls can conceal meaningful differences. This inspector identifies common zero-width characters, bidirectional control marks, mixed-script text, and a small set of Greek or Cyrillic characters that resemble ASCII letters.

Why use Unicode security inspector?

A suspicious identifier, hostname, command, or code review change can appear harmless while containing characters that change how people or tools interpret it. A visible report gives reviewers a practical starting point for investigation.

When to use Unicode security inspector

Use it before sharing source snippets, reviewing an unfamiliar identifier, investigating a copy-paste problem, or checking text that looks visually inconsistent. Mixed scripts are often legitimate in natural-language content, so treat findings as review prompts rather than proof of malicious intent.

How to use Unicode security inspector

Paste the exact text, including whitespace, into the inspector.

  1. Inspect the text: Paste text without normalizing or retyping it so character positions remain accurate.
  2. Review positions: Compare each code point and its position with the original text.
  3. Decide intent: Check whether mixed scripts or invisible controls are required by the language or format.
  4. Normalize or replace: Remove accidental formatting marks and use clear ASCII identifiers where project conventions require them.

Key features

  • Invisible character detection: Flags common zero-width spaces, joiners, direction marks, and byte-order marks.
  • Bidi control reporting: Reports bidirectional controls that can change visual ordering.
  • Script and confusable checks: Highlights mixed Latin, Greek, and Cyrillic text plus common ASCII lookalikes.

Common use cases

  • Code review: Inspect a suspicious filename, comment, string literal, or identifier.
  • Paste debugging: Find a zero-width character that breaks matching, validation, or shell commands.
  • Security triage: Review a pasted URL or account name that resembles a trusted value.

Examples

Zero-width space

api​Key
Reports U+200B Zero-width space between api and Key.

Cyrillic lookalike

pаypal
Reports Cyrillic U+0430, which resembles ASCII a.

Technical reference

Findings describe code points, not the sender's intent.

Zero-width space
U+200B has no visible width but can change string equality and word boundaries.
Bidi controls
Directional formatting characters affect visual order and deserve careful review in source code.
Mixed scripts
Text that combines scripts may be legitimate prose but is risky in short identifiers or hostnames.
Confusables
Characters can look alike without being identical code points; this tool reports common examples only.

Common mistakes to avoid

Assuming mixed scripts are always malicious

Why it happens: Many languages naturally require a non-Latin script.

How to avoid it: Focus scrutiny on identifiers, domains, commands, and context where an ASCII lookalike matters.

Retyping suspicious text before inspection

Why it happens: Retyping can silently remove the character that caused the problem.

How to avoid it: Copy the original bytes or text exactly, then inspect positions.

Using visual comparison alone

Why it happens: Different code points can render the same in a chosen font.

How to avoid it: Compare reported U+ code points and normalize identifiers deliberately.

Frequently asked questions

Does a finding mean the text is unsafe?

No. It indicates a character worth reviewing in context.

Can this find every Unicode confusable?

No. It flags common cases and is not a complete Unicode security policy.

Why inspect source code comments?

Bidirectional controls can affect how nearby source appears to a reviewer.

Is the input sent anywhere?

No. Inspection occurs locally in the browser.

References

Privacy and availability

  • Runs entirely in your browser — zero server processing
  • No signup or account required
  • Works offline once loaded
  • Fast, lightweight, no external dependencies
  • Available as a browser extension for Chrome and Firefox