AP style checker: free and AI tools compared (and what they miss)

AP style is the set of writing and editing rules published by The Associated Press in the AP Stylebook, the standard reference for U.S. news writing. If you need the rules themselves, start with the AP style guide and the numbers, dates and times cheat sheet. This page gives you a test you can run on any checker, the answer key, and a prompt you can reuse.

The best AP style checker by use case

What each tool actually does

AP StyleGuard

Sold by Lingofy AS, AP StyleGuard checks copy against AP Stylebook rules as you type in Word, Outlook and PowerPoint, with a version for web-based editors. It needs a paid subscription. AP first launched a Word style checker in 2011.

Tansa

A proofing system for newsrooms and publishers, with an AP style option. AP has described Tansa Systems as a technology partner. It is sold to organizations.

PerfectIt

An editing add-in that checks consistency: hyphenation, capitalization, abbreviations and spelling variants. Its built-in style sheets are Chicago, European Union, United Nations, Australian Government, GPO, American Legal and WHO. AP isn't one of them; PerfectIt says you can customize a style sheet to follow any manual, so you build the AP sheet yourself.

Grammarly style guides

Grammarly's style guide feature holds custom rules for "the proper use, spelling, and formatting of specific words, terms, and phrases." Its help center lists it on Pro, Plus, Business and Enterprise plans: one rule set on Pro, up to 50 on Business. Grammarly doesn't document a built-in AP rule set, so you enter rules such as "health care → healthcare" yourself. Word swaps work; rules that depend on sentence position (titles, sentence-start numbers) don't.

AI chatbots (ChatGPT, Claude, Gemini)

With a precise prompt, a chatbot catches most number, date and time errors. It also states rules that don't exist, applies rules that changed (the % sign in 2019, healthcare in 2026) and rewrites sentences you didn't ask it to touch.

WriteOrbit proofreading

No AP rule engine. Its AI review covers proofreading and tone; for AP style, run the prompt below in the AI chat beside the document.

The test: one paragraph, 20 planted AP errors

To compare checkers fairly, we wrote one 300-word news paragraph with 20 AP errors and nine traps: phrases that look wrong but are correct AP style. A good checker catches the errors and leaves the traps alone. The story, people and book are fictional.

Copy the paragraph exactly as it appears here into each tool.

The Harbor Food Collective, a nonprofit pantry at 1200 Main Street in Salem, OR, will open its new warehouse at 10:00 a.m. November 14. Volunteers will serve coffee, toast, and ham and eggs to the first 50 guests, and mayor Jane Ortiz will cut the ribbon. The collective expects to feed ten more families each week, a rise of five percent over last year. 15 families are already on its waiting list. "We have outgrown the old building," said Daniel Okafor, the collective's executive director. Mr. Okafor said the city's health care clinic next door is okay with the longer hours. The warehouse cost $2,000,000, most of it from a state grant and a fund drive that began Sept. 30. Over 200 households used the pantry last month, and the collective will add 3 delivery vans for residents who can't leave home. A seven-year-old volunteer, Nora Pike, has sorted cans, boxes, and jars every weekend since the spring. At a board meeting, Okafor read a passage from Lena Marsh's novel The Salt Orchard, which he said shaped the group's mission. The collective also uses artificial intelligence software to forecast demand, and Okafor said the AI forecasts have cut food waste by a third since the summer. Doors will close at 12 noon on Saturdays and at 7 PM on weekdays, when most volunteers are free to help. The Mayor said the city would work towards opening a second site on the east side in the 2030s, once the state grant program is renewed. Until then, the collective plans to run a mobile pantry from a church parking lot two afternoons a week, and it is asking local grocers to donate fresh produce that would otherwise go unsold at the end of the week. The mobile pantry will start in January.

Answer key: the 20 errors

The nine traps (correct AP style; a flag here is a false positive)

Scoring

Count a catch only if the fix is the AP form ("10:00 AM" for "10:00 a.m." is a miss). Count a false positive for each trap flagged and any change that makes correct copy wrong. Run AI tools twice in fresh chats and report the lower score.

Results

Why no checker catches everything

Most AP rules are patterns a tool can match: ":00," "PM," a two-letter state code after a comma. The rest depend on meaning, and that's where every checker slips.

A reusable AI prompt for AP style checking

Paste this into any AI chat, then paste your text below it. It works in ChatGPT, Claude, Gemini or the AI chat beside a WriteOrbit document. The recent-changes list is there because models often learned older AP rules.

You are an AP style copy editor. Check the text below against the current
AP Stylebook (58th edition, 2026). Do not rewrite for tone or content.
Change only what AP style requires.

Apply these current rules, which override anything you learned earlier:
- Use the % sign with figures (5%), not "percent" (changed 2019).
- "healthcare" is one word (changed 2026).
- Spell out state names in story text; AP abbreviations (Calif., not CA)
  only in datelines, captions, tables and lists. Never abbreviate Alaska,
  Hawaii, Idaho, Iowa, Maine, Ohio, Texas, Utah.
- "over" and "more than" are both correct with numbers (changed 2014).
- No serial comma in a simple series; use it when an item contains "and"
  or when leaving it out would confuse.
- One through nine in words, 10 and up in figures; ages, money, %, times,
  dates, dimensions, speeds, temperatures and scores always in figures.
  Spell out a number that starts a sentence, except a year.
- Jan., Feb., Aug., Sept., Oct., Nov., Dec. with a date; never abbreviate
  March to July. No st/nd/rd/th. 10 a.m., 3:30 p.m., noon, midnight.
- Capitalize formal titles only directly before a name; no Mr./Mrs./Ms.
  except in quotes; last name only on second reference.
- Composition titles (books, films, songs, TV shows, games) in quotation
  marks, not italics.
- Spell out "artificial intelligence" on first reference; AI after that.
- Em dashes with a space on each side; ellipsis as " ... ".

Output a table with these columns:
# | Original text | AP style fix | Rule broken | Confidence (high/medium/low)

Rules for your answer:
1. List every error. Do not list anything that is already correct.
2. If a fix depends on context you can't see (publication date, whether
   a phrase is a title, house style), put it in a separate list called
   "Needs a human check" instead of the table.
3. If you are not sure a rule exists, mark the row "low" and say so.
4. After the table, give the corrected text with only these changes made.

Text:
[PASTE YOUR TEXT HERE]

Using the prompt as an AP style converter

To convert copy from Chicago or a house style into AP, change the first paragraph to: "Convert the text below from [Chicago / our house style] to AP style. List every change in the table before giving the converted text." The change table matters most: it lets an editor approve each edit instead of trusting a rewrite.

The human checklist for what tools miss

Run this after any tool, on the printed page or a fresh screen.

• Every title before a name is capitalized and, where AP abbreviates it, abbreviated (Gov., Sen., Rep.).
• Every title after a name or standing alone is lowercase.
• Every person is named in full once, then by last name only. No Mr. or Ms. outside quotes.
• Every book, film, song, show and game title is in quotation marks.
• The dateline uses capitals and the AP state abbreviation; the story spells the state out.
• Days of the week are used only for dates within seven days of publication.
• Every percentage change says whether it's percent or percentage points.
• House-style exceptions are applied.

Checking AP style in WriteOrbit

WriteOrbit is a writing editor, not an AP checker. A reporter and editor use it for the AP pass like this:

1. Open the draft, or the newsroom .docx (styles are kept).
2. Run the AP prompt in the AI chat beside the document, so the error table sits next to the text.
3. Run the proofreading review. Each issue lands as a comment on the exact phrase.
4. Fix as suggestions (tracked changes), so the writer can accept or reject "5 percent → 5%." Version history keeps the original.
5. Do the human checklist, then export to Word or PDF.

The free plan includes a few AI chat messages and review checks a day, enough to try this on one story. Check pricing for current limits.

FAQ

Is there a free AP style checker?

Not a complete one. The AP-licensed checkers, such as AP StyleGuard, are paid. The best free option is a general AI chatbot given a detailed AP prompt, like the one on this page, followed by a human read for context rules. Free websites that call themselves AP checkers vary widely, so test any of them on a paragraph with known errors first.

Does Grammarly check AP style?

Not as a built-in AP rule set. Grammarly's help documentation describes its style guide feature as custom rules your team writes, on paid plans: one rule set on Pro, up to 50 on Business. You could enter AP rules yourself, but Grammarly doesn't ship the AP Stylebook, so it won't know AP's titles, datelines or recent changes.

Can ChatGPT check AP style?

It can catch many mechanical AP errors if you give it a precise prompt, but it also invents rules and may use outdated ones, such as "percent" (replaced by % in 2019) or "health care" (one word since 2026). Ask it to cite the rule for each fix, put recent changes in the prompt, and check every fix it's unsure about against the Stylebook.

What is the most accurate AP style checker?

Tools built on the AP Stylebook itself, such as AP StyleGuard and newsroom systems like Tansa, have the most AP rules. None of them can judge context: whether a title comes before a name, whether a phrase is a composition title, or whether a date falls within seven days. A human read remains the last pass.

What is an AP style converter?

An AP style converter rewrites text from another style, such as Chicago or a house style, into AP style: numbers, dates, titles, commas and composition titles. No converter is reliable without review. The safest way is the AI prompt on this page in "convert" mode, with every change listed so an editor can approve it.

Next step

A checker is only as good as the rules you know. Learn the 25 rules editors fix most in the AP style guide, and keep the AP numbers, dates and times cheat sheet open while you edit.

Sources

1. StyleGuard (Lingofy AS), product site: https://styleguard.com/
2. StyleGuard shop, AP Stylebook products: https://shop.styleguard.com/
3. Poynter, "AP introduces style check for Microsoft Word" (Dec. 15, 2011): https://www.poynter.org/reporting-editing/2011/ap-introduces-style-check-for-microsoft-word
4. Tansa: https://www.tansa.com/
5. PerfectIt support, "Does PerfectIt support other styles such as AMA, APA, AP, etc.?": https://support.perfectit.com/kb/guide/does-perfectit-support-other-styles-such-as-ama-apa-ap-etc-WHKuds7V14/Steps/2298078
6. Grammarly Support, style guide feature: https://support.grammarly.com/hc/en-us/articles/360043832652
7. ACES: The Society for Editing, "AP announces Stylebook changes; healthcare tops list" (2026): https://aceseditors.org/2026/04/24/ap-announces-stylebook-changes-healthcare-tops-list/
8. Poynter, "AP says the percentage sign is now OK when used with a numeral" (2019): https://www.poynter.org/reporting-editing/2019/ap-says-the-percentage-sign-now-ok-when-used-with-a-numeral-thats-shift5/
9. The Associated Press, AP Stylebook: https://www.apstylebook.com/