AP Title Case: Which Small Words Stay Lowercase?
In AP-style title case, the words that stay lower case are the articles (a, an, the), the coordinating conjunctions of three letters or fewer (and, but, or, for, nor, so, yet) and the prepositions of three letters or fewer (such as at, by, in, of, on, to and up). Everything else is capitalised, and so is any word, however short, when it is the first or last word of the title. That is the rule the AP-style output of the Title Case Converter applies.
The rule is simple; the edge cases are where people get stuck. This guide lists exactly which words the converter keeps lower case, runs real titles through it, and marks the places where you still need to make a correction by hand.
Where the AP rule comes from, and where it applies
The Associated Press Stylebook uses this rule for composition titles: the names of books, films, songs, reports, talks and similar works. It is widely borrowed for blog headlines and page titles because it is short and easy to apply. It is worth knowing that AP does not use it for its own news headlines, which are written in sentence case (first word and proper nouns capitalised, nothing else). If you want that look instead, see title case or sentence case for headlines.
Other style guides draw the line elsewhere. The best-known difference is the Chicago Manual of Style, which lowercases prepositions whatever their length, so a Chicago title has "with", "from" and "through" in lower case where an AP title capitalises them. Neither is wrong. Pick the one your site uses and stick to it.
The words the converter keeps lower case
The converter holds a fixed list of 22 short words. In AP-style output, each is lower case unless it is the first or last word of the title:
| Group | Words kept lower case |
|---|---|
| Articles | a, an, the |
| Coordinating conjunctions | and, but, or, for, nor, so, yet |
| Short prepositions | as, at, by, in, of, off, on, out, per, to, up, via |
"For" appears once in the list but works as both a conjunction and a preposition; either way it is three letters and stays lower case. Words not on the list are capitalised, which is why short verbs such as "is", "be" and "do" come out as "Is", "Be" and "Do". That is correct: AP lowercases only the small function words, never verbs.
Titles that come out right
| Typed as | AP-style output |
|---|---|
| what to write in a title tag and what to leave out | What to Write in a Title Tag and What to Leave Out |
| how to check a title tag with a pixel counter | How to Check a Title Tag With a Pixel Counter |
| writing for the web, from the top down | Writing for the Web, From the Top Down |
| the one rule to live by | The One Rule to Live By |
| where does the title come from? | Where Does the Title Come From? |
| life as a copy editor | Life as a Copy Editor |
A few things to notice. "With" and "From" are capitalised because they have four letters; under AP that is right. "Out", "By" and "From" are capitalised at the ends of their titles because the last word always is. "The" opens the fourth title with a capital for the same reason at the other end. The question mark does not stop "From" being treated as the last word.
Five places to correct the converter by hand
1. Brand names, and acronyms typed in lower case
The converter keeps any word you type in capitals (two letters or more) exactly as you typed it, so acronyms such as SEO, URL, HTML and PDF come through unchanged in every style. It has no list of brand names, though: every other word gets a capital first letter and lower case for the rest. "SEO for iPhone apps: what to put in the title" comes out as "SEO for Iphone Apps: What to Put in the Title", where the correct AP title is "SEO for iPhone Apps: What to Put in the Title". Restore every name with internal capitals (iPhone, WordPress, YouTube, LinkedIn) after you copy the output.
Two cases still need watching. An acronym typed in lower case ("seo") is treated as an ordinary word and comes out as "Seo". And a title typed entirely in capitals is converted word by word, acronyms included, because the converter cannot tell a shouted headline's words from acronyms: "HOW TO WRITE A TITLE TAG FOR SEO" becomes "How to Write a Title Tag for Seo". Type the title in normal case with its acronyms in capitals and they survive.
2. A short word after a colon
The converter treats a colon like any other punctuation, so a short word after it stays lower case: "headlines: a style guide for small teams" becomes "Headlines: a Style Guide for Small Teams". Most house styles, and most readers, expect "Headlines: A Style Guide for Small Teams", treating the part after the colon as the start of a subtitle. Capitalise that word by hand if your style follows this convention.
3. Hyphenated compounds
The AP-style output capitalises only the first letter of a hyphenated word: "a step-by-step guide to follow-up emails" becomes "A Step-by-step Guide to Follow-up Emails", and "per-word rates and up-to-date fees" becomes "Per-word Rates and Up-to-date Fees". Style guides differ in their detailed rules for hyphenated compounds, but a common approach is to capitalise each main part and keep short function words inside the compound lower case: "Step-by-Step", "Follow-Up", "Per-Word", "Up-to-Date". Choose a rule and fix these by hand. (The converter's plain Title Case output goes the other way and capitalises every part, giving "Step-By-Step".)
4. Small words used as adverbs
The list is matched word by word with no grammar, so "off", "on", "out" and "up" are lowered even when they are part of a phrasal verb rather than a preposition. "turn it off and on again" comes out as "Turn It off and on Again". In "turn off" and "turn on", those words are adverbs, not prepositions, so the AP rule does not lowercase them; most editors would write "Turn It Off and On Again". The same applies to "Leave Out" in the middle of a title, "Sign Up" and "Log In". When a short word belongs to the verb, capitalise it.
5. Words the list does not know
Only the 22 words above are ever lowered. Short words outside the list, such as "if", "vs" and "into", are always capitalised. "Into" has four letters, so that matches AP. "If" is a two-letter conjunction, and style guides and editors do not all treat it the same way, so check it against your house style; "vs." is a house-style decision too. Words longer than three letters are capitalised, which matches AP.
A quick check you can run on any title
- Paste the title into the converter and copy the AP-style line.
- Scan for brand names, and any acronym you typed in lower case, and restore their capitals.
- Look after any colon and capitalise the first word if your style asks for it.
- Decide each hyphenated compound against your house rule.
- Read the title aloud and capitalise any "off", "on", "out" or "up" that belongs to the verb.
- If the title is going in a title tag, check its width in the Headline Pixel Counter. Capitals are wider than lower-case letters, so the final cased version is the one to measure; equal character counts can give quite different widths.
What the converter does not cover
- Grammar. It cannot tell a preposition from an adverb or a verb particle.
- Proper nouns. It knows no names or brands, and it keeps an acronym only when you typed it in capitals.
- Other style guides. Its title-case output applies the core AP rule only. For Chicago, MLA or APA titles, lowercase the extra words those guides require (for Chicago, prepositions of any length) by hand.
- Sentence-level decisions. It does not choose between title case and sentence case for you, and it does not rewrite the words.
- Languages other than English. Capitalisation conventions in other languages are different, and the word list is English only.
Used this way, the converter saves the tedious part (getting 22 small words right every time) and leaves the judgement calls to you.