String Length / Byte Size Analyzer

Free online string length and byte size analyzer. Instantly count characters, words, lines, UTF-8 bytes, digits, letters, whitespace, emojis, and Unicode code points.

More free online text tools — no install required.

What String Length / Byte Size Analyzer Does

Takes raw text input and outputs a structured report: JavaScript .length character count, Unicode-aware character count via Array.from(), UTF-8 encoded byte size, word count, line count, whitespace count, letter count, digit count, and emoji count. A secondary mode outputs a per-character index with each character's Unicode code point in U+XXXX format.

Who Uses This Tool

String Length / Byte Size Analyzer is built for Backend developers enforcing database column byte limits, API engineers validating payload size constraints, frontend developers debugging character counter UIs, QA engineers testing form field validation, localization engineers handling multibyte languages, security researchers inspecting obfuscated strings. Whether you are processing data as part of an automated pipeline or need a quick one-off conversion in your browser, the tool requires no installation and no account — paste your input and get your result in seconds.

Primary Use Case

Checking the exact UTF-8 byte size of a string before storing it in a database column with a byte-based length constraint such as VARCHAR(255).

The Problem It Solves

Developers manually calling Buffer.byteLength() in Node or strlen() in C-based systems risk silent truncation when multibyte characters (accented letters, CJK, emoji) make byte size exceed character count. Copying text into a character-count widget gives a false safe result. This tool exposes the byte size directly, eliminating truncation bugs without writing throwaway code.

Example

Input
Hello
Output
Characters: 5
Unicode Characters: 5
UTF-8 Bytes: 5
Words: 1
Lines: 1
Whitespace Characters: 0
Letters: 5
Digits: 0
Emoji Characters: 0

When to Use This Tool

Use this tool when validating text limits, estimating payload sizes, analyzing Unicode strings, preparing API requests, or debugging encoding and storage constraints.

What to Do With the Output

Paste byte count into database schema documentation, use character count to set maxlength attributes on input fields, feed word count into CMS character limit validators, use Unicode breakdown output to debug encoding pipelines or log parsers

Common Mistakes to Avoid

Assuming character count equals byte count — any non-ASCII character uses 2–4 bytes in UTF-8. Emoji count only matches the regex range U+1F300–U+1FAFF; some emoji outside that range (e.g. ©, ✅) are not counted. Line count always returns at least 1 even for single-line input because split(/\r\n|\r|\n/) always produces one element. The validate button confirms the text is encodable as UTF-8 but does not check encoding correctness of the source — browser strings are always UTF-16 internally. Unicode breakdown index is zero-based and may not match byte offset positions.

How It Works

Character count uses String.length, which counts UTF-16 code units. Unicode character count uses Array.from(text).length, which iterates by Unicode code point and correctly handles surrogate pairs. UTF-8 byte size is measured via TextEncoder().encode(str).length with a unescape(encodeURIComponent()) fallback. Words are matched with /\S+/g. Lines are split on \r\n, \r, or \n. Letters, digits, whitespace, and emoji are each extracted with dedicated regex patterns. Unicode breakdown maps each code point via codePointAt(0) converted to uppercase hex.

Pro Tip

Paste minified JSON or JWT payloads into the Unicode breakdown mode to instantly spot non-printable or invisible Unicode characters (zero-width spaces, right-to-left marks) injected into strings — each appears as its own indexed entry with a distinct code point, exposing hidden characters that standard text editors render invisibly.

Also Known As

String Length / Byte Size Analyzer is also commonly referred to as string byte length calculator, text byte size checker, UTF-8 length tool, character byte counter, string size in bytes, strlen online, byte count string, unicode string analyzer, text metrics tool, multibyte character counter, string inspector. All of these terms describe the same conversion — no matter what you call it, this tool handles it.

Frequently Asked Questions

Non-ASCII characters encode to more than one byte in UTF-8. An accented character like é is 2 bytes, a CJK character is 3 bytes, and most emoji are 4 bytes. The tool reports both counts so you can see the difference directly.
"Characters" is String.length, which counts UTF-16 code units. Emoji and some rare characters are represented as two code units (a surrogate pair), making String.length return a higher number. "Unicode Characters" uses Array.from() to count actual code points, giving the human-visible character count.
No. All browser strings are UTF-16 internally and are always encodable as UTF-8. The validate button confirms encoding succeeds without throwing, which will always pass for normal input. It is most useful for detecting if a string contains characters that fail encodeURIComponent in the fallback path.
Splitting any string on newline delimiters always produces at least one element, so the minimum line count is 1. A blank input throws an error before reaching the count logic.
No. The regex covers the Unicode range U+1F300–U+1FAFF. Older emoji that fall outside this range — such as © (U+00A9), ✅ (U+2705), or ⭐ (U+2B50) — are not counted in the emoji field but are still counted in the total character and Unicode character fields.
Yes, but with a caveat: MySQL's VARCHAR(255) means 255 characters by default, not 255 bytes, when the column character set is utf8mb4. If your column uses a byte-based limit (common in legacy schemas or specific storage engines), use the UTF-8 Bytes value from this tool to verify the string fits within that constraint.