Base64 Encoder and Decoder
Encode and decode UTF-8 text as standard or URL-safe Base64.
UTF-8 Validator
Validate hexadecimal byte sequences as strict UTF-8. Detect invalid continuation bytes, truncated sequences, overlong encodings, surrogate values and out-of-range code points.
Paste hexadecimal bytes such as 48 65 6C 6C 6F. Input is validated as bytes, not normalized text.
UTF-8 validation results
Validate UTF-8 bytes online
This UTF-8 validator accepts hexadecimal byte sequences, parses the bytes first, and then enforces strict modern UTF-8 rules. It detects malformed continuation bytes, truncated sequences, overlong encodings, encoded surrogate values and code points above U+10FFFF. For valid input, it shows byte counts, code-point counts, a decoded preview, normalized hexadecimal and UTF-8 BOM status.
This is a server-side validator. The submitted byte sequence is sent to UnicodeNow for analysis; it is not a browser-local tool.
UTF-8 validation example
Input:
48 65 6C 6C 6F 2C 20 63 61 66 C3 A9 20 F0 9F 98 80Expected result:
Status: Valid UTF-8
Decoded text: Hello, café 😀
Bytes: 17
Code points: 13
BOM: NoneWhat makes UTF-8 valid?
ASCII bytes 00-7F stand alone. Multi-byte sequences begin with a valid leading byte and must contain the exact number of continuation bytes in the range 80-BF. Modern UTF-8 uses one to four bytes, requires the shortest valid form, excludes UTF-16 surrogate code points, and does not allow values above U+10FFFF.
Common UTF-8 errors
| Example | Error |
|---|---|
80 | Unexpected continuation byte at byte 1. |
C3 28 | Invalid continuation byte at byte 2. |
F0 9F 98 | The four-byte sequence starting at byte 1 is truncated. |
C0 AF | Overlong UTF-8 encoding. |
ED A0 80 | UTF-8 cannot encode surrogate code points. |
F4 90 80 80 | The sequence represents a value above U+10FFFF. |
F4 8F BF BF | Valid UTF-8 for maximum Unicode scalar value U+10FFFF. |
Supported hexadecimal input formats
The parser accepts separated byte groups, continuous hexadecimal, 0x-prefixed values, comma-separated values and whitespace across lines. Every parsed value must represent one byte from 00 to FF.
48 65 6C 6C 6F
48656C6C6F
0x48 0x65 0x6C 0x6C 0x6F
48,65,6C,6C,6FUTF-8 BOM handling
The UTF-8 BOM is EF BB BF. It is valid but optional. This validator treats it as a BOM only at the start, preserves the original byte count, reports UTF-8 BOM detected, and excludes the leading BOM character from the decoded preview.
Valid UTF-8 vs safe text
UTF-8 validation checks byte structure. Valid UTF-8 can still contain null bytes, control characters, bidirectional formatting controls, zero-width characters, noncharacters or private-use characters. Those are content warnings, not structural UTF-8 errors. Valid UTF-8 is not automatically safe for HTML, SQL, logs, terminals, source code or other contexts.
How to use the validator
- Paste hexadecimal byte values into the input field.
- Run the UTF-8 validation.
- Review the validity status and any error position.
- For valid input, inspect the decoded preview and BOM result.
- Copy or download the validation report if needed.
Privacy and server processing
The submitted byte sequence is sent to UnicodeNow for UTF-8 validation. Input is processed securely and is not intentionally retained after the request completes.
Do not submit passwords, private keys, access tokens, personal records or other sensitive data.
Frequently asked questions
What is valid UTF-8?
Valid UTF-8 is a byte sequence that follows the modern one-to-four-byte encoding rules, uses valid continuation bytes, avoids overlong forms, excludes surrogate code points and stays within U+10FFFF.
How do I validate UTF-8 bytes?
Paste hexadecimal bytes into the validator and run the check. The server parses the hex first, then validates the resulting byte sequence as strict UTF-8.
What is an invalid continuation byte?
A continuation byte must be in the range 80-BF. If a multi-byte sequence contains a different byte where a continuation byte is required, the sequence is invalid.
What is a truncated UTF-8 sequence?
A sequence is truncated when a leading byte announces a multi-byte character but the input ends before all required continuation bytes appear.
What is an overlong UTF-8 sequence?
An overlong sequence uses more bytes than necessary for a code point. Modern UTF-8 rejects non-shortest encodings such as C0 AF.
Can UTF-8 encode surrogate code points?
No. UTF-16 surrogate code points from U+D800 through U+DFFF are not Unicode scalar values and cannot be encoded in valid UTF-8.
What is a UTF-8 BOM?
A UTF-8 BOM is the leading byte sequence EF BB BF. It is valid but optional, and this validator reports it only when it appears at the start.
Can valid UTF-8 still contain control characters?
Yes. UTF-8 validation checks byte structure. Valid text can still contain null bytes, controls, bidi controls or invisible characters, which are reported separately as warnings.
Does this tool decode valid input?
Yes. When input is valid UTF-8, the result includes a decoded text preview. The preview is rendered as text, not HTML.
Is my input stored on the server?
The submitted byte sequence is sent to UnicodeNow for validation and is not intentionally retained after the request completes. Do not submit secrets or sensitive data.
Related tools
To decode valid hexadecimal bytes, use Hex to Text. To compare possible legacy encodings, use the Character Encoding Detector.
Binary to Text
Decode binary byte groups into UTF-8 text.
Byte Length Calculator
Count UTF-8 bytes, code points, grapheme clusters and UTF-16 code units for text.
Character Encoding Detector
Compare likely text encodings from raw bytes or byte-like input.
Decimal to Text
Convert decimal bytes or Unicode code point values to text.
Hex to Text
Decode hexadecimal byte values into UTF-8 text.
UTF-8 Encoder and Decoder
Convert text to UTF-8 bytes and validate byte sequences.
Text to Hex
Convert UTF-8 text bytes into hexadecimal values.
Related guides
Learn why valid UTF-8 can appear broken when decoded incorrectly in What Is Mojibake?. For a repair workflow, read How to Fix Broken UTF-8 Text.
Unicode vs UTF-8
Unicode defines characters and code points. UTF-8 encodes those code points as bytes for files, databases, web pages, APIs and network messages.
UTF-8 vs UTF-16
Compare UTF-8 and UTF-16 with byte examples, surrogate pairs, byte order, BOM behavior and practical guidance for developers.
What Is Mojibake?
Learn why text becomes garbled, how UTF-8 bytes turn into mojibake such as café and It’s, and how to repair it safely.
How to Fix Broken UTF-8 Text
A safe workflow for diagnosing broken UTF-8, validating bytes, reversing mojibake, handling double encoding and auditing repairs.