Unicode to UTF-8 Online

UTF-8 Explained

This Unicode to UTF-8 converter online maps characters to UTF-8 byte sequences for debugging APIs, file encodings, and i18n tests. UTF-8 (8-bit Unicode Transformation Format) is a variable-length character encoding for Unicode and a type of prefix code. See UTF-8 on Wikipedia and the Unicode Standard.

It can encode all valid Unicode code points using one to four bytes. Since lower-value code points are generally used more frequently, encoding everything with a fixed width would be inefficient and wasteful of memory.

UTF-8 was designed for backward compatibility with ASCII. The first 128 Unicode characters are encoded using a single byte with the same binary values as ASCII, making them byte-for-byte identical. This means software that originally handled ASCII can continue to work with little or no modification.

Unicode to UTF-8 Converter Workflow

Use this page as a Unicode to UTF-8 converter:

1. Paste text or a single character into the input
2. View the Unicode code point (per MDN codePointAt)
3. Inspect the UTF-8 byte sequence in binary and hex
4. Copy results for debugging APIs, file encodings, or i18n tests

Batch paste is supported for short strings; very long input may be truncated in the preview for performance.

UTF-8 Code Point Prefix Table

The 128 ASCII characters require only one byte. Latin characters with diacritics, Greek letters, etc., require two bytes. Most commonly used characters in the BMP (including most CJK characters) use three bytes. Characters in supplementary planes (such as emoji) use four bytes.

Encoding Process

1. Convert the character to its Unicode code point (e.g., str.codePointAt(0))
2. Determine the number of bytes needed based on the prefix table
3. Apply the appropriate prefix and fill in the code point bits from right to left
4. Group every eight bits to produce the UTF-8 byte sequence

For example, "道" has code point 0x9053, requiring three bytes. With the prefix 1110xxxx 10xxxxxx 10xxxxxx, filling in the bits yields 11101001 10000001 10010011, which is E9 81 93.

Input Characters to View UTF-8 Encoding

Type any character or text into the input field, and the tool will display the UTF-8 byte sequence for each character. Results are shown in hexadecimal format so you can see how many bytes each character occupies.

Understanding Variable-Length Encoding

UTF-8 is a variable-length encoding — different ranges of characters use different numbers of bytes:

The advantage of this design is that pure English content is fully ASCII-compatible, with each character taking only 1 byte. Other languages' characters require more space, but all Unicode characters can be represented.

CJK Character Encoding

Each CJK character occupies 3 bytes in UTF-8. This is useful knowledge for estimating text file sizes:

"你好世界" (Hello World in Chinese)
你 → E4 BD A0 (3 bytes)
好 → E5 A5 BD (3 bytes)
世 → E4 B8 96 (3 bytes)
界 → E7 95 8C (3 bytes)
Total: 12 bytes

A 1,000-character pure Chinese article is approximately 3 KB in UTF-8. If it contains English and numbers, the actual size will be smaller.

Practical Use Cases

File Encoding

When saving code or text files, UTF-8 is the most widely used encoding format today. If CJK characters appear garbled in a file, it's usually because the file was actually encoded in GBK or another encoding but was read as UTF-8. Inspecting the byte sequence with this tool can help you determine the file's true encoding.

HTTP Headers

In web development, you frequently need to declare the encoding in Content-Type:

Content-Type: text/html; charset=utf-8

If the byte stream returned by the server doesn't match the declared encoding, the browser will display garbled text.

Database Field Length

MySQL's VARCHAR(255) with utf8mb4 encoding stores up to 255 characters (not bytes). However, the underlying storage must account for each character's byte size — CJK characters take 3 bytes each, emoji take 4 bytes each. Understanding this helps you design field lengths appropriately.

URL and JSON Encoding

CJK characters in URLs are first converted to their UTF-8 bytes, then percent-encoded. For example, "你" in UTF-8 is E4 BD A0, which becomes %E4%BD%A0 in a URL. This tool can help you verify whether the conversion is correct.

API

JavaScript

You can use the built-in TextEncoder API for UTF-8 encoding and decoding in JavaScript:

export function stringToUint8 (s: string): Uint8Array {
  const enc = new TextEncoder()
  return enc.encode(s)
}

export function uint8ToString (uint8: Uint8Array): string {
  const enc = new TextDecoder()
  return enc.decode(uint8)
}

Python

> 'hello'.encode()
b'hello'

> b'\xe4\xbd\xa0\xe5\xa5\xbd'.decode()
'你好'

FAQ

Q: Why is UTF-8 the most popular encoding on the internet?

UTF-8 has several key advantages that have made it the de facto standard. First, it is fully backward-compatible with ASCII — all ASCII characters have identical encodings in UTF-8, meaning vast amounts of existing English content require no conversion. Second, UTF-8 uses variable-length encoding (1 to 4 bytes), making it very space-efficient for English text while still covering all Unicode characters. Additionally, UTF-8 has no byte-order issues and doesn't require a BOM, simplifying cross-platform transmission. Currently, over 98% of web pages use UTF-8 encoding.

Q: Can UTF-8 represent all Unicode characters?

Yes. UTF-8 can encode all code points in the Unicode standard (U+0000 to U+10FFFF), including characters within the Basic Multilingual Plane (BMP) and those in supplementary planes (such as emoji, historic scripts, and rare CJK characters). Characters outside the BMP use 4-byte encoding. As the Unicode standard continues to add new characters, UTF-8's encoding mechanism can fully accommodate them — there are no characters it "can't encode."

Q: How many bytes does a Chinese character take?

In UTF-8, a common Chinese character occupies 3 bytes. This is because most Chinese characters fall within the BMP range of Unicode (U+4E00 to U+9FFF), which corresponds to UTF-8's 3-byte encoding region. A small number of rare CJK characters (such as those in Extension B and later) are in supplementary planes and require 4 bytes. By comparison, the same Chinese character takes only 2 bytes in UTF-16 and 2 bytes in GBK/GB2312. This is why UTF-8 is slightly less storage-efficient than UTF-16 and GBK for pure CJK text.

Q: Does UTF-8 have a BOM?

UTF-8 can have a BOM (EF BB BF), but it is not recommended. The BOM (Byte Order Mark) was originally designed for UTF-16 to indicate byte order. Since UTF-8 has no byte-order issue, the BOM serves no practical purpose. However, some Windows editors (such as Notepad) add a BOM to UTF-8 files by default, which can cause issues like shell scripts failing to execute, JSON parsing errors, or PHP outputting unexpected characters. Unix/Linux environments and modern development tools universally use UTF-8 without BOM.

Q: How can I determine whether a file is encoded in UTF-8?

There is no 100% reliable method, but you can check from several angles. First, look for a UTF-8 BOM (EF BB BF) at the beginning of the file — if present, it's definitely UTF-8. Second, you can validate the file content against UTF-8 encoding rules — UTF-8 multi-byte sequences have strict format requirements (fixed high-bit patterns in the leading byte and continuation bytes), and random non-UTF-8 data typically fails validation. On the command line, you can use the file command (e.g., file --mime-encoding filename) to detect the encoding. In code, you can try decoding with UTF-8 — if it succeeds without errors and the content looks reasonable, you can be fairly confident it's UTF-8.

Q: How do I convert Unicode to UTF-8 with this tool?

Paste the character or string, then read the code point and byte sequence shown below the input. The steps mirror the encoding algorithm in the WHATWG Encoding standard and MDN UTF-8: determine code point → pick 1–4 byte template → fill continuation bits → output hex bytes.