Non-Breaking Space U+00A0

The non-breaking space (NBSP, U+00A0) is the best-known invisible character on the web. Developers type it as  ; writers paste it from Word without knowing. It looks exactly like a regular space, but it stops the line from breaking there, so the words on either side stay together.

That makes it useful for typography. It also causes a classic bug: two strings that look identical fail to match because one has non-breaking spaces where the other has regular ones.

Common Uses

• Keeping words together. Numbers and units (100 km), titles and names (Dr. Smith), and page references (page 7) should not split across lines.
• Extra whitespace in HTML. Browsers collapse multiple regular spaces into one but keep non-breaking spaces, which made   the classic way to add spacing.
• Blank usernames. Some platforms accept NBSP in a username, which makes the profile name look blank.
• French typography. French rules call for a non-breaking space before semicolons, colons, question marks, exclamation marks and some quotation marks, so the punctuation never starts a line.
• Empty table cells. In HTML, empty table cells may collapse to zero height.   keeps them at their proper height.

How to Type

The macOS Trap

Hold Option for a special character, hit Space before letting go, and you get NBSP instead of a space. The code looks right but fails. Many invisible bugs in code written on a Mac start here.

Why NBSP Causes Bugs

Non-breaking space (U+00A0) and regular space (U+0020) are different Unicode characters that look identical. So:

• String comparison fails. "hello world" === "hello\u00A0world" is false, though both show "hello world" on screen.
• Search and find/replace miss it. Searching for a space will not find non-breaking spaces.
• JSON parsing can break. NBSP in a JSON key, or where regular whitespace is expected, can make parsers throw errors.
• CSS selectors can fail. A class attribute with NBSP instead of a regular space becomes one class name instead of two.
• Regular expressions differ. \s matches NBSP in some regex flavors but not others.
• Trimming may not work. Some languages' trim() strips regular spaces but leaves NBSP.

How to Detect NBSP in Code

In JavaScript:

// Check if a string contains NBSPtext.includes('\u00A0')
// Replace all NBSP with regular spacestext.replace(/\u00A0/g, ' ')
// Or use the broader approach - replace all Unicode spacestext.replace(/[\u00A0\u2000-\u200A\u202F\u205F\u3000]/g, ' ')

Where NBSP Sneaks Into Your Text

NBSP rarely gets into text on purpose. The usual sources:

1. Microsoft Word. Word can insert NBSP automatically, for example before colons, question marks and other punctuation in French text.
2. Google Docs. Text copied out of Google Docs can contain NBSP, especially around formatted or consecutive spaces.
3. Web pages. HTML that uses   for spacing pastes as real NBSP characters.
4. macOS Option+Space. The most common accidental source for developers.
5. AI chatbots. Text copied from ChatGPT and other AI tools can contain NBSP and its narrow cousin U+202F (see below).
6. CMS rich text editors. WordPress, Contentful and other CMS editors often insert NBSP when you type consecutive spaces or leave empty paragraphs.
7. PDF text extraction. Text copied from PDFs often has NBSP instead of regular spaces.

The "ChatGPT Watermark": Hidden Spaces in AI Text

In April 2025, the AI-detection startup Rumi reported that ChatGPT's newer models (o3 and o4-mini at the time) were inserting narrow no-break spaces (U+202F), mostly into longer outputs. The finding spread as a "ChatGPT watermark" for catching AI-written essays.

OpenAI told Rumi the characters were not a deliberate watermark but "a quirk of large-scale reinforcement learning." NNBSP is also legitimate typography, for example in French, so its presence alone proves nothing. Either way, these spaces break string matching, validation and diffs just like a regular NBSP. Before you paste AI output into code, spreadsheets or CMS fields, run it through the Invisible Character Viewer: it shows every U+00A0 and U+202F and strips them in one click.

NBSP vs Other Space Characters

Mixing these up causes different bugs. See the Zero-Width Space (zero width, allows line breaks, the opposite of NBSP), the Word Joiner (U+2060, prevents line breaks like NBSP but with no width) and the Em Space (the width of the letter M). Narrow No-Break Space (U+202F) is the thinner NBSP used in French typography and the character behind the "ChatGPT watermark" story.

For Web Developers

Before you reach for  , check whether CSS does the job better:

• Layout spacing: use CSS margin or padding.
• Keeping words together:   works, or put CSS white-space: nowrap on a wrapping element.
• Empty table cells: use CSS empty-cells: show.

Using   for visual layout is a code smell. Reserve it for keeping words together.