What the replacement options do
The dropdown is the control that matters. Pick what each dash becomes and the whole document updates in one pass.
Comma, the default: most AI em dashes sit mid-sentence, marking an aside a comma handles cleanly. The rhythm survives and the tell goes.
Period: for the dash that splices two complete sentences together. Two sentences read better, and the AI cadence leaves with the dash.
Hyphen: a casual swap for chat and informal writing. It reads cheap in polished prose, so use the comma there.
Nothing at all: delete the dash when the sentence already flows without a mark. Check the spacing around the edit once before you send it.
En dash handling is a separate toggle, on by default, following whichever replacement you chose. Turn it off to keep en dashes in number ranges, where they are correct. Smart quotes, ellipses and invisible characters stay untouched here. The AI text cleaner handles those in the same pass as the dashes.
Why AI text is full of em dashes
You can cut the problem off before it starts. Open ChatGPT's Personalization, then Custom Instructions, and add a line such as "don't use em dashes; use commas or periods". OpenAI shipped a dedicated toggle for this on November 14, 2025, and Sam Altman called it a "small-but-happy win". Users still report the occasional dash getting through.
Prevention only covers text you wrote yourself. Anything pasted from a colleague, a PDF, a slide deck or a different model was never under your settings, so it needs cleaning after the fact.
Models learned the habit from their training data. Edited books and prestige magazines lean on the em dash, and the model absorbed that style with no keyboard nudging it back toward plain punctuation. One measurement put ChatGPT at roughly 8 to 12 em dashes per 1,000 words, against a typical human rate near 3.
The habit is stubborn. Research measuring dash rates found some models still emitting around 4 per 1,000 words when told explicitly to avoid them. That persistence comes from how the models were tuned after training.
Which kills the watermark theory. People spotted odd invisible spaces in ChatGPT output in April 2025 and called it a secret tracker. OpenAI told reporters the characters were not a watermark:
a quirk of large-scale reinforcement learning
The behavior vanished after a model update a day later. Em dashes work the same way. A style quirk you can tune at the source, never a hidden signal.
Em dash vs en dash vs hyphen
Three marks, three jobs, and width separates them. The em dash runs about the width of a capital M, the en dash the width of an N, the hyphen shortest of all.
Em dash ("—", U+2014): breaks and asides, the widest of the three. The one AI overuses.
En dash ("–", U+2013): ranges and spans, 2010–2015 or pages 40–52. Keep it wherever it means "to".
Hyphen ("-"): joins compound words, well-known or twenty-two. It lives inside words, never between clauses.
How to use it
1. Paste your text into the box above. Model output, a Word document, a PDF or a web page all work the same.
2. Pick a replacement from the dropdown. Comma is the default, and the en dash toggle rides along with it.
3. Copy the result. Character and word counts update as you work, so you can check the length.
This free tool vs Klipto
The web tool fixes one snapshot. Clean AI drafts a few times a day and the copy-to-site-copy-back loop gets old, so on a Mac you can get it automatically on every paste with Klipto instead. Its Anti-LLM transform strips dashes and the rest of the AI tells on every ⌘V, offline, in any app.
| This free web tool | Klipto Anti-LLM | |
|---|---|---|
| Removes or replaces em and en dashes | Yes, manually | Yes, on every paste |
| Choice of hyphen, comma, space, remove | Yes | Dashes become hyphens |
| Runs on paste | No, paste into the site and copy back | Yes, every ⌘V |
| Works system-wide (Slack, Notion, Word, code) | No, this page only | Yes, any macOS app |
| Also strips smart quotes and hidden characters | No, see the AI text cleaner | Yes, full Anti-LLM pass |
| Needs a website or internet | Yes | No, native and offline |
| Privacy | Runs in your browser | On-device, network only for updates |
| Clipboard history, Stack, 20+ transforms | No | Yes |
| Platform | Any browser | macOS 14+ |
| Price | Free | Free tier, $19.99 one-time Pro |