Document & Markup Converter
About UTF-8 Validator
The Comprehensive UTF-8 & Unicode Byte Sequence Validator checks text files and byte arrays for invalid UTF-8 sequences, corrupted multibyte codepoints, surrogate pairs, overlong encodings, and Unicode replacement characters (`\uFFFD` ).
How to Use UTF-8 Validator
Step 1
Paste text or upload a document into the UTF-8 validator.
Step 2
Click "Validate UTF-8".
Step 3
Review the encoding verdict, byte health status, and flagged error offsets.
Step 4
Click "Copy Report".
Practical Use Cases for UTF-8 Validator
Diagnosing Corrupted Unicode & Mojibake in Databases
Locate invalid byte sequences, Latin-1 double encoding artifacts, and replacement characters (``) in database export files.
Validating File Uploads for Strict UTF-8 Compliance
Verify that user-submitted CSV and XML files strictly conform to the UTF-8 specification before downstream backend processing.
Input & Output Examples
Validating Text with Corrupted Unicode Replacement Character
Text: "Caf\uFFFD Paris"
Status: ⚠️ Issues Found (1 Replacement Character `\uFFFD` detected at char index 3 | Text is well-formed UTF-8 but contains placeholder glyphs)
Key Features & Performance
- ✓Detects: Invalid UTF-8 bytes, Unpaired UTF-16 surrogate pairs, Overlong byte encodings, and Replacement Characters (``).
- ✓Highlights exact line numbers and byte offsets where encoding errors occur.
- ✓Displays full Unicode Codepoint breakdown (e.g. `U+00E9` for 'é') and byte length metrics.
- ✓100% Client-Side memory execution.
- ✓1-Click Copy validation audit report.
Key Terminology & Definitions
UTF-8 (8-bit Unicode Transformation Format)
The dominant variable-width character encoding for the web, capable of encoding all 1,112,064 valid character code points in Unicode using one to four 8-bit bytes.
Replacement Character (`U+FFFD` )
A special Unicode symbol used by browsers and decoders to replace an incoming character whose value is unknown or unrepresentable in Unicode.