Substack Notes vs. Twitter/X: What's Actually Different

Published: September 2026

At a glance, Notes and X look like the same product: a scrolling feed of short posts, with likes, replies, and reposts (restacks, in Substack's terminology). The surface similarity is real, but the two platforms reward different things and attract a different kind of reader, which matters more than the interface similarities for anyone deciding where to spend their time.

The obvious differences first

A few mechanical distinctions worth knowing:

• Length: X caps non-Premium posts at 280 characters. Substack Notes has no enforced limit, though the practical ceiling for what actually gets read is much shorter than the technical max.
• Media: X natively supports video, GIFs, and polls. Substack has been closing this gap (Notes can now include video), but the format range is still narrower on Notes.
• Scale: X is a vastly larger platform in raw user count - by some estimates over 100x the size of Substack's total audience. Reach potential is structurally different before you've written a single word.

None of these differences are the main reason to pick one platform over the other, though - the real difference is who's actually reading.

The audience is fundamentally different

Substack Notes' most active users skew heavily toward other writers and creators, not a general audience the way X's user base does. This matters directly: a platform whose most engaged users are other publishers behaves differently than one whose most engaged users are the general public. On Notes, restacking someone's Note in front of your own subscriber base is a meaningfully different action than retweeting on X, because there's a higher chance the person seeing it is themselves a writer who might subscribe, not just scroll past.

A real head-to-head experiment

One creator ran a direct comparison: for one week, he published to Substack Notes first, then republished the same or adapted content to Twitter the next day, using AI to condense longer Notes into tweet-length versions where needed (Creator Experiments). The results were lopsided: Notes drove more new email subscribers in that single week than Twitter had produced across his entire prior time on the platform, and engagement (likes and comments) ran 1.5–2x higher on Notes than the Twitter versions of the same content.

The honest caveat, which the author included himself: his Substack following was already substantially larger than his Twitter presence at the time, following a multi-year gap in posting there. This wasn't a controlled, audience-matched experiment - it's a real data point from one creator's specific circumstances, not proof Notes universally outperforms X for everyone. But it's a useful directional signal, especially combined with the audience-composition difference above: if your goal is specifically growing email subscribers, a platform whose power users are other writers is structurally better positioned to help with that than one whose power users are a general audience there for entertainment or news.

What this means for where you post what

A practical way to think about the split:

• Newsletter growth specifically - Notes has the structural advantage, since its power users are more likely to become subscribers themselves, and Substack's own algorithm is explicitly built to convert readers into subscribers, which isn't X's business model at all.
• Raw reach and general audience visibility - X's much larger user base gives it an edge if the goal is exposure beyond people already interested in newsletters, or a topic with mainstream, non-writer appeal.
• Fast, real-time commentary - X's culture and infrastructure (retweets, quote tweets, trending topics) are more built for reacting to something happening right now than Notes is.

For most Substack writers, this isn't really an either/or decision - it's about which platform gets which kind of content. A Note built around "here's an insight from my niche" fits Notes' writer-heavy audience well. A quick reaction to a trending topic outside your specific niche might actually reach more people on X.

Repurposing between the two

If you're already writing for Notes, the condensing-with-AI approach from the experiment above is a reasonable way to also post on X without doubling your writing time - take a Note, compress it to fit X's shorter format, and treat it as a distribution channel rather than a place you draft original content for. This connects to the broader repurposing framework covered elsewhere on this blog - the same underlying idea, formatted for wherever it's going.

The bottom line

Notes and X aren't really competing for the same job. If subscriber growth is the specific goal, the writer-dense audience and subscription-optimized algorithm on Notes give it a real structural edge - the one documented head-to-head comparison backs this up, caveats included. If broad, general-audience reach matters more than newsletter conversion specifically, X's scale is hard to match. Most creators end up using both, with Notes as the primary channel for anything meant to convert a reader into a subscriber.

See exactly how your Notes are performing, regardless of what else you post elsewhere. NotesIQ tracks your real Substack Notes engagement and growth.