How to Stop Claude Using Em Dashes

Claude uses em dashes to connect related ideas, add emphasis, and set off parenthetical information. This comes from its training data, which includes a lot of professionally edited text where em dashes are common. If your writing style does not use them, or your house style rules them out, you can give Claude a direct instruction to stop. Saving that instruction in fenbs means it applies to every session without you repeating it.

A clear punctuation rule works better than asking Claude to write more plainly. Plain does not mean no em dashes. A punctuation rule removes the ambiguity.

Why Claude uses em dashes so often

Claude was trained on a large body of text that includes journalism, books, and edited online writing. Em dashes are a common choice in that writing. They signal a pause, a qualification, or a parenthetical remark, and Claude uses them in roughly the same way.

There is no setting to turn off em dash usage. It is a stylistic tendency that you override with an explicit instruction. Claude responds well to punctuation rules when they are clear and specific.

The instruction that works

The most reliable instruction is: "Do not use em dashes. Use a comma, period, or parentheses instead." Add it at the start of a conversation or include it in your project instructions or custom settings.

Some variations that work well in practice:

• "Do not use em dashes in any form. Rewrite those sentences with a comma or period."
• "Avoid em dashes throughout. A colon or parentheses can replace most of them."
• "Use no em dashes or en dashes. Plain punctuation only: commas, periods, colons, semicolons."

Be direct. A vague request for "simpler punctuation" does not reliably remove em dashes, because em dashes can feel simple to Claude.

How to check and revise existing text

If Claude has already written a passage with em dashes, ask it to revise the specific text. Paste the passage and give the instruction: "Rewrite this without any em dashes. Replace each one with a comma, a period, or parentheses, whichever reads most naturally."

You can also ask Claude to go through the text systematically: "Find every em dash in this passage and tell me what you would replace it with, then make those replacements." This is useful when you want to review the changes before accepting them.

What to expect from the instruction

Claude follows explicit punctuation instructions reliably in most cases, but it is not perfect. In a long conversation, earlier instructions can carry less weight as the context fills up. If em dashes reappear, a brief reminder in your next message usually corrects it.

Claude will occasionally still use an em dash when it feels like the only natural option. If you need strict compliance, asking Claude to review its output for em dashes at the end is a useful extra step: "Before you send this, check your draft for any em dashes and replace them."

How to make the rule permanent

Claude.ai has custom instructions under Preferences. Add the no-em-dash rule there and it applies to every new conversation automatically.

In Claude Code, add the rule to CLAUDE.md or AGENTS.md at the root of your project. Claude Code reads those files at the start of every session.

For a team, a shared writing style record in fenbs covers every AI app the team uses. One entry is enough, and any team member can read or update it. For related prompts from the Claude family of models, what is Claude AI covers how the product line fits together.

What to do when Claude slips back

Even with the no-em-dash instruction in place, Claude can revert in a long conversation where earlier instructions fade. When that happens, a direct reminder in your next message usually fixes it. "You have been using em dashes. Please stop and revise the last response to remove them."

You can also ask Claude to proofread its own output before sending it: "Before you finalize this, scan for any em dashes and replace each one with a comma, period, or parentheses." Building the check into the task catches most slips without an extra round trip.

For team writing, a shared writing style rule in fenbs means every connected assistant starts each session with the same punctuation preference. One person updating the rule updates it for everyone, instead of each team member maintaining their own copy.

How to do this with fenbs

1. Create a free account and set up a project for the work where writing style matters.
2. Open Skills and prompts and add a new entry. Title it "Writing style" and include your punctuation rules, including the em dash instruction.
3. Connect your AI apps from Integrations. Claude, ChatGPT, Cursor and other connected apps can list and read your saved prompts.
4. At the start of a session, ask the assistant to read your skills. It will apply the writing rules without you retyping them each time.
5. If the rule is a team standard, add it to Decisions and rules instead. Rules appear at the top of the AI context that connected assistants read.