Why Does ChatGPT Use So Many Em Dashes? (And How to Remove Them)

The short answer

ChatGPT uses a lot of em dashes for three reasons that stack on top of each other.

First, the training data. Books, magazines, newspapers and carefully edited web writing use em dashes far more often than casual writing does. Chat messages, comments and quick emails mostly use commas, full stops or nothing at all. A language model learns the distribution it is shown, so it reproduces the punctuation of polished prose, including the dash.

Second, preference tuning. After pretraining, models are refined using human feedback, where raters compare candidate answers and the preferred ones are reinforced. Raters tend to favor answers that read as fluent, confident and finished. The em dash is a cheap way to sound that way: it adds emphasis, sets off an aside or tacks on a punchy clause without any extra effort.

Third, flexibility. An em dash lets the model join two clauses without committing to a comma, a semicolon or a period. When the next words are uncertain, a dash is a safe connector that is rarely grammatically wrong.

Put plainly, this is a statistical habit. It is not a watermark, and it is not a deliberate signature added by OpenAI. If you want to know what actually does get copied along with ChatGPT text, see does ChatGPT watermark text.

Em dash, en dash, hyphen: what ChatGPT is actually typing

People call it "the ChatGPT dash" or "the hyphen thing," but there are three different characters involved:

• — is the em dash, U+2014. It is the long one.
• – is the en dash, U+2013. It is shorter and normally used for ranges such as 2024–2026.
• - is the plain hyphen-minus, U+002D, the one on your keyboard.

What ChatGPT produces in running prose is almost always the em dash, U+2014, with no spaces around it, as in: The result was clear—and surprising. A human typing quickly would more often write The result was clear - and surprising. with a spaced hyphen, which is a different character entirely.

Is the em dash proof that text is AI-written?

No. Journalists, novelists, essayists and academic writers have used em dashes for a long time, and style guides cover them in detail. A document full of em dashes might be AI output, or it might be written by an editor who likes them. Treating the character as proof will produce false accusations.

The reverse is also true. A text with no em dashes tells you nothing about who or what wrote it. AI detectors look at many signals, mostly statistical properties of the writing, and punctuation of a single kind is not enough to decide anything on its own.

The pattern is also weakening as a tell. Since late 2025, ChatGPT follows a custom instruction to avoid em dashes more reliably than it used to, so plenty of AI-assisted text now comes out without them. Do not build a workflow on spotting them.

How to stop ChatGPT from using em dashes

The most durable fix is a custom instruction, set once in your ChatGPT personalization settings. Wording that works well is short and gives alternatives:

Do not use em dashes. Use commas, periods or parentheses instead.

For a single conversation, put the same sentence at the end of your prompt. If a reply still contains one, ask for a rewrite: Rewrite that with no em dashes. That usually fixes the whole reply in one pass.

One caveat: style instructions can fade in long chats. If dashes creep back after many messages, repeat the instruction or start a fresh conversation. Instructions reduce the habit, but they do not guarantee that none will slip through, so a final check is still worth doing.

How to remove em dashes from text you already have

The quickest route is our em dash remover. Paste your text, pick a replacement (comma, hyphen with spaces, plain hyphen, or remove), clean it and copy the result. It also strips hidden characters and converts smart quotes in the same pass, so you do not need separate cleanup steps. Everything runs in your browser and nothing is uploaded.

If you would rather do it by hand, Find & Replace works in Word and Google Docs. Search for — and replace it with a comma followed by a space (, ). In Word you can paste the dash into the search box or use the Special menu; in Google Docs, open Find and replace with Ctrl+H or Cmd+Shift+H.

For developers, a one-liner in JavaScript does the same job, including any spaces around the dash:

text.replace(/\s*—\s*/g, ", ")

Note that this replaces every em dash with a comma, which is not always the right choice, as the next section explains. For broader cleanup of pasted AI output, the AI text cleaner handles hidden characters and formatting in one go.

Which replacement should you pick?

Comma is the right default for most prose. It works when the dash was joining two clauses or introducing a short continuation.

A spaced hyphen ( - ) keeps the pause and the rhythm. Use it when the break in the sentence matters, for example in a headline or a casual note.

Removing the dash suits cases where it was purely decorative. If the sentence reads fine with the two halves simply joined by a space, or split into two sentences, take it out.

Keep it and rewrite when the dash marks a true parenthetical, a pair of dashes wrapping an aside. Replacing both with commas can make the sentence ambiguous. Use parentheses, or restructure the sentence so the aside is its own clause.