The em dash and ChatGPT: what ten years of Reddit posts show

What we counted

We took 100 large English-language subreddits and looked at every text post and every comment of at least 200 characters written there from January 2016 to September 2026. That comes to 15,817,377 posts and 241,541,185 comments. For each one we checked a single thing: does it contain at least one em dash (Unicode U+2014, the long dash) anywhere in it. For posts, the title counts too.

Hyphens and en dashes don't count. The 200-character cut is there because a one-line comment rarely has room for any dash, and thousands of short replies would bury the signal. Posts and comments get the same cut, so the two lines on the chart stay comparable. How we picked the subreddits is in the method section.

The climb started in August 2024, not when ChatGPT launched

ChatGPT became public on November 30, 2022. In that quarter, 0.83% of long posts in our sample had an em dash, about where the share had been all year. Over the next 18 months it crept up to 1.19%.

The jump came in August 2024. In July, 1.28% of long posts had an em dash; in August, 1.95%; by December, 3.12%. In July 2025 it reached 6.83%, the highest month in more than ten years of data. By quarter, the peak is Q2 2025 at 6.53%, 9.4 times the level of early 2021.

We can't tie the August jump to any particular release, and timing is all this data shows: it came three months after OpenAI released GPT-4o and about 20 months after ChatGPT launched. Most of the rise happened in the twelve months that followed.

Em dashes in comments rose far less

Reddit comments are mostly typed straight into the comment box, on the same phones and keyboards people use for posts. If a keyboard or an app had started inserting em dashes on its own, comments would show it too.

Comments did rise. Between Q2 2024 and Q2 2025 the share of long comments with an em dash went from 0.65% to 1.32%, a gain of 0.67 percentage points. Long posts gained 5.35 points over the same year, going from 1.19% to 6.53%. Since then comments have stayed between 1.10% and 1.24%.

Posts are where people paste in text they wrote somewhere else: a story drafted in a notes app, a launch announcement cleaned up in a chatbot. That's the most likely reason the two lines split, though it's an inference from the pattern and not something we can observe.

Is it autocorrect? What the 2017 iPhone change looked like

Autocorrect is the usual objection, and it has changed Reddit's punctuation once already. In September 2017 Apple shipped iOS 11 with Smart Punctuation turned on by default, which converts two typed hyphens into an em dash. Daring Fireball was already complaining about it during the beta.

Our data picks it up. Between Q3 2017 and Q2 2018 the em dash share rose by 0.24 percentage points in posts and 0.18 in comments, while the double hyphen, the old way to type a dash, fell in both. When the keyboard changes, both kinds of text move together.

The 2024 rise looks different. Double hyphens in posts were at 0.40% in Q2 2024 and 0.40% a year later, and comments gained 0.67 points against 5.35 for posts.

Em dashes rose in every subreddit with enough posts

A big change in a few busy subreddits could draw a curve like this by itself, so we checked subreddit by subreddit. 72 subreddits in the sample had at least 300 long posts both in 2021 and in 2026. The em dash share in posts went up in all 72 and at least tripled in 60. For comments we used the 81 subreddits with at least 3,000 long comments in both years: the share went up in 78 but tripled in only 28.

In the median subreddit, 0.50% of long posts had an em dash in 2021 and 4.00% in 2026. For comments the median went from 0.42% to 0.81%. In 67 of the 69 subreddits that pass both thresholds, posts gained more than comments. Taken together, the 72 subreddits give almost the same quarterly curve as the full sample: 0.69% in Q1 2021, 6.49% in Q2 2025 and 5.71% in Q3 2026.

A few communities stand out. In r/SideProject, where people announce things they've built, 29.3% of long posts in 2026 contain an em dash, up from 2.0% in 2021. r/writers started high, as you'd expect from people who care about punctuation, and still went from 2.7% to 13.8%.

How often Reddit comments mention em dashes

For years almost nobody on Reddit talked about em dashes. In these 100 subreddits, between 12 and 69 comments a quarter used the words "em dash" from 2016 through September 2024. Then came 127 in Q4 2024, 320 in Q1 2025 and 2,575 in Q2 2025. Per million comments, the count went from about 2 in mid 2024 to 83.

What happened after the July 2025 peak

By month, the peak came in July 2025, when 6.83% of long posts had an em dash. In August the share fell to 5.70%, 17% lower in a single month, and in December 2025 it reached 4.78%. Long comments fell over the same step, from 1.31% in July to 1.04% in August.

August 2025 is the month GPT-5 became ChatGPT's default model, taking over from GPT-4o. In mid-November, OpenAI's CEO said ChatGPT now follows custom instructions to leave out em dashes, and the following month was the lowest since the peak. That's the order of events. This data can't show that either change caused the drop.

The fall wasn't limited to a few busy communities. Of the 74 subreddits with at least 300 long posts in July 2025 (5 or more of them with an em dash), 63 had a lower em dash share in August, and the median one dropped to 0.82 of its July level. It doesn't look like a summer dip either: from 2016 to 2024, the July to August change in posts ranged from 8% down to 52% up.

The em dash jokes don't explain it on their own, at least not by timing. Comments that mention em dashes peaked in May 2025 (1,168 that month), while the share in posts kept climbing into June and held there in July.

Other big monthly drops, and what shipped that month

The table lists the four largest month-to-month drops since the peak, next to what changed in ChatGPT around the same time. Most of them line up with a release, but that is weaker evidence than it looks: OpenAI shipped something new in most months of this period, and GPT-5.4 came out in March 2026, a month when the share went up. Only August 2025 really stands out. It's the biggest drop, it came in the month the default model changed, and no July to August change in the nine years before it comes close.

In 2026 the monthly share has stayed between 5.09% and 6.26%, still seven to nine times the early 2021 level. Em dashes in titles kept growing: in Q2 2024, 0.12% of long posts had one in the title; by Q2 2025 it was 1.00%, and in Q3 2026 1.22%.

Do posts with an em dash do worse on Reddit now?

This part uses a wider set: the full list of 400 subreddits our sample was drawn from, and their long text posts from 2019 to September 2026. For each post we know whether it made the top 10% of its subreddit that month by our engagement score. The top 10% is measured against every post in the subreddit, links and images included, so long text posts land there less than 10% of the time. We compared how often posts with an em dash made it against how often you'd expect, given the subreddit and the month. A ratio of 1 means no difference.

From 2019 to 2021, posts with an em dash did better. They reached the top 10% 1.44 times as often as expected for their subreddit and month. In raw numbers, 11.9% of them made it, against 7.5% of long posts without one. Our guess is that people who bothered with proper punctuation also wrote more careful posts, but this data can't test that.

By 2026 that edge is gone: the ratio is 0.96. With the em dash in the title it's 0.87, and it's below 1 in 123 of the 188 subreddits where we had at least 50 such posts to measure. That doesn't mean the dash itself hurts a post. Posts with em dashes may simply be different posts now.

What this data can't tell you

• An em dash doesn't mark a post as AI-written. People typed them long before chatbots: 0.70% of long posts in early 2021, and far more in some communities. The change shows up across millions of posts and says nothing reliable about any one of them.
• Timing isn't cause. The rise came while AI writing tools were spreading, and the comment and double-hyphen checks rule out the obvious alternatives we could test. Other explanations are still possible.
• The 100 subreddits were picked by how active they are today, and some were small or didn't exist yet in 2016. The fixed group of 72 subreddits in the subreddit section is there to check for that.
• October 2025 looks odd. Its em dash share in posts (6.39%) sits well above September (5.34%) and November (5.56%), and we haven't found out why. It's left out of the monthly chart, and without it Q4 2025 would be 5.18% instead of 5.56%. Nothing in this article depends on that month.
• Post counts jump in Q3 2023: the number of long posts in the sample goes from 356,158 to 557,160 in one quarter. The em dash share barely moves (0.86% → 0.91%), so the jump doesn't drive the trend.
• The latest quarter has more comments than usual: 43.1 million in Q3 2026 against 33.8 million a quarter earlier, and we haven't found out why. The em dash share in long comments doesn't jump with it (1.24% → 1.15%), but we don't draw conclusions from Q3 2026 alone.
• En dashes rose too. In posts, the en dash went from 0.45% in Q2 2024 to 2.63% in Q3 2025. We haven't looked into why.

Method

Subreddits

We started from the 400 most active English-language subreddits with at least 200,000 subscribers, leaving out NSFW and non-public ones, ranked by recent posting volume. The 100 in this study are every fourth subreddit on that list, so the sample runs from the busiest communities down to ones with a few hundred thousand subscribers.

Posts and comments

Posts are text posts (not link or image posts) with a body of at least 200 characters; removed, deleted and pinned posts are excluded. A post counts as having an em dash if its title or body contains the character U+2014. Comments need at least 200 characters, and deleted ones are excluded.

For the "em dash" mentions we count comments of any length that contain "em dash", "em-dash" or "emdash", ignoring case. A double hyphen is " -- " with spaces around it, or two hyphens between letters. The en dash is U+2013.

Time

Each post and comment goes into a month and a quarter by its creation time in UTC. The data runs from January 1, 2016 to September 30, 2026. On the line charts each value sits at the end of its month or quarter, and releases sit on their actual dates.

The top 10% comparison

Our engagement score ranks each post against the other posts in its subreddit that month. For every post with an em dash, the top-10% rate of its subreddit and month is its expected value. We add those up and divide the actual number of top posts by that sum, which takes care of some subreddits and months being easier than others.

Source

Public Reddit archives back to 2005, plus our own collection for recent months. All counts come from one set of queries run on October 23, 2026. If you spot a mistake, tell us and we'll fix it here with a dated note.

The data

The monthly, quarterly and per-subreddit counts behind this article are in these files, along with the top-10% comparison. They're free to reuse under CC BY 4.0; please credit KissMyPost and link to this page.

• CSVQuarterly counts, 2016 to Q3 202643 quarters. Long posts and long comments with em dash, en dash and double hyphen counts, plus comments that mention "em dash".
• CSVCounts by subreddit, 2021 and 2026All 100 subreddits in the sample: long posts and long comments, with and without an em dash, for 2021 and January to September 2026.
• CSVMonthly counts, January 2016 to September 2026Long posts and long comments with and without an em dash, plus comments that mention "em dash", by month. October 2025 is flagged as a suspected data issue.
• CSVTop 10% comparison by period, 2019 to 2026Posts with an em dash against the expected top-10% count, for the whole post and for the title, with the number of subreddits above and below 1. Includes the 2022 to 2023 period we leave out of the article.
• PNGMain chart, 1600 × 1000The chart at the top of this page as an image.

Questions people ask

What we're looking at next

Next we're measuring how often commenters say a post was written by AI. It's far more common than it was in 2022 and still rising every quarter. You can follow along through the RSS feed or the research page.

This study comes from the archive behind KissMyPost, a Reddit analytics tool. It shows what kind of posts do well in a subreddit, who writes there and when, and lets you search posts back to 2005.