Is it “seat belt” or “seatbelt”?

Use “seat belt” (two words) in most formal writing; major dictionaries and news style guides—including AP and Chicago via Merriam-Webster—prefer the open compound. “Seatbelt” (one word) appears in informal contexts and some brand or regional usages, but it is less common in edited, general-audience prose. This article explains how authorities treat the term, where the one-word form shows up, and how to choose the right spelling for your context.

What major references say

The following list summarizes how prominent style guides, dictionaries, and official sources write the term, helping you align with widely accepted standards.

• AP Stylebook: seat belt (two words).
• Chicago Manual of Style (via Merriam-Webster): seat belt (two words).
• Merriam-Webster: seat belt (primary entry as two words).
• Oxford English Dictionary and Oxford Learner’s Dictionaries: seat belt (two words; the closed form appears in some publications but is not the main headword).
• Cambridge Dictionary: seat belt (two words).
• Collins English Dictionary: seat belt (two words; notes “seatbelt” as a variant in some contexts).
• U.S. National Highway Traffic Safety Administration (NHTSA): seat belt (two words) in official communications.
• UK government guidance: seat belt/seat belts (two words) in legal and public information pages.

Taken together, these authorities indicate “seat belt” is the prevailing standard in edited English on both sides of the Atlantic, even though the one-word variant appears in some outlets and is understandable to readers.

Regional and industry usage trends

In U.S. and UK newsrooms, “seat belt” remains the norm. The closed form “seatbelt” is more likely in casual writing, on social media, or in some automotive marketing and model-feature names. While British publications may show “seatbelt” more often than American ones, official UK materials still largely use “seat belt.” If you’re writing for a publication, follow its house style; if in doubt, choose the two-word form.

Why compounds vary

English compounds often evolve from open (“seat belt”) to hyphenated (“seat-belt”) to closed (“seatbelt”) over time. Not every term completes that cycle, and institutional style can keep an open form in place for decades. Today, “seat belt” is still the editorial default, with “seatbelt” an acceptable but secondary variant in less formal contexts.

How to choose in your writing

Use the checklist below to decide quickly which form fits your context and whether any hyphenation is needed when the term modifies another noun.

1. Follow your style guide: AP, Chicago, and most newsroom guides prefer “seat belt.”
2. Default for general audiences: “seat belt” is safest and widely recognized.
3. Match institutional usage in specialized contexts: Legal texts and government pages typically use “seat belt”; brand materials may opt for “seatbelt.” Check and mirror the source.
4. As a modifier: “seat belt reminder,” “seat belt law,” and “seat belt use” generally do not need a hyphen. Add a hyphen only if it prevents real ambiguity.
5. Grammar and capitalization: Plural is “seat belts.” Capitalize only at the start of a sentence or in a title; it’s not a proper noun.

If you’re unsure and have no house style to consult, choosing “seat belt” will align with most editorial standards and reader expectations.

Examples

These examples illustrate preferred usage in sentences you might encounter in news, policy, or everyday writing.

• Always wear your seat belt.
• The car’s seat belt reminder chimed at 15 mph.
• State seat belt laws vary by jurisdiction.
• Less preferred in formal news copy: “Always wear your seatbelt.”

In formal or edited contexts, these examples show that “seat belt” reads naturally and aligns with standard references, while the one-word variant is better reserved for informal settings or brand-led usage.

Bottom line

“Seat belt” is the standard spelling in mainstream style guides, dictionaries, and official communications. Use “seatbelt” only if you’re following a specific house style or brand convention that calls for it.

Summary

Preferred: “seat belt” (two words). Variant: “seatbelt” (one word) appears informally and in some marketing or regional usage but is not the dominant editorial form. When in doubt, choose “seat belt.”

Is it seat belt or seatbelt?

Both “seat belt” (two words) and “seatbelt” (one word) are accepted spellings for the vehicle safety device, though “seatbelt” is the more common spelling today and is preferred by some style guides and dictionaries, while others still favor the open form. Ultimately, either spelling is understood by most people, so you can choose the one that feels most natural to you or that aligns with the style guide you are following. 
Here’s a breakdown of the spellings:

• Seat belt (two words): Opens in new tabThis is the open compound form, which was the original spelling. It’s still seen in some style guides, such as the Associated Press Stylebook, and many dictionaries. 
• Seatbelt (one word): Opens in new tabThis is the closed compound form and is more common in contemporary usage, especially in American English. Dictionaries like the Collins Dictionary also list “seatbelt”. 

Why there’s a difference:

• Compound word evolution: Words often evolve from separate words into hyphenated words and finally into closed compounds as they become more common and integrated into the language. 
• Style guide preferences: Different style guides have different rules, with some preferring open compounds for certain words, while others accept or even prefer closed compounds. 
• Regional differences: Some suggest that splitting compounds is more common in American English than in British English, though both spellings are understood globally. 

Is seatbelt one word or two words?

“Seatbelt” can be written as either one word or two words, but the two-word form, “seat belt,” is more widely accepted and preferred by many dictionaries and style guides, especially in American English and journalism. While the single word “seatbelt” is also in use and generally understood, sticking to the two-word “seat belt” is the safest bet for clarity. 
Reasons to Use “Seat belt” (Two Words)

• Widely Accepted: Most dictionaries and style guides, including Merriam-Webster and the Associated Press (AP) Stylebook, prefer “seat belt”. 
• Consistency: Using the two-word form helps maintain consistency with other similar compound words that are still written as two words, such as “safety belt”. 
• Journalistic Standard: The AP Stylebook, a key reference for journalists, specifically states that “seat belt” is two words. 

When You Might See “Seatbelt” (One Word)

• In British English: Opens in new tabThe one-word form is more common in British English and is recognized by dictionaries like Collins Dictionary. 
• Common Usage: Opens in new tabDespite style guide preferences, “seatbelt” is still in common usage and is generally understood. 

Recommendation
For clear and widely accepted communication, especially in an American English context, use “seat belt”.

What is a seat belt also called?

life belt, safety belt, safety harness.

What do Americans call a seat belt?

n. A safety strap or harness designed to hold a person securely in a seat, as in a motor vehicle or aircraft. Also called safety belt. The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers.