Facebook, Instagram and TikTok Ad Character Limits (and Why AI Keeps Ignoring Them)
The numbers are short. The interesting part is that stating them to a language model does almost nothing unless you state them a particular way — which is why so much AI-written ad copy arrives too long to run.
The limits
| Platform | Headline | Body / primary text |
|---|---|---|
| 40 | 125 | |
| 40 | 125 | |
| TikTok | 40 | 100 |
| Google Search | 30 | 90 |
These are the working limits we generate to. Facebook and Instagram will accept longer primary text than 125 characters — the field allows far more — but the feed truncates it behind a "See more" fold on mobile, which is where most of your impressions are. Writing to 125 means the whole message is visible without a tap.
Google Search is the strict one: 30 and 90 are hard ceilings, and the editor will not save a character over.
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Use the tool free →Truncation is not the same as rejection
Four different things happen to over-length copy, and only one of them is an error you will notice:
- Google refuses to save it. You find out immediately.
- Facebook and Instagram accept it and hide the overflow behind "See more". Your call to action can end up on the wrong side of that fold.
- TikTok overlays the caption on the video, where long text competes with the footage for the same space.
- Everywhere, a headline that fits on desktop can wrap or clip on mobile.
So an ad can be "accepted", run, spend money, and still be quietly cut in half for most of the people who see it. That is the failure worth designing against.
Why AI-written copy overruns
Because of how the limit is usually communicated to the model.
Buried mid-prompt as prose — "Facebook ad: max 40 char headline, max 125 char primary text, conversational tone" — the limit reads as a style note alongside the tone instruction, and gets weighted about as heavily. We measured this on our own generations: a sample of nine variants came back nine out of nine over the limit, by between 16 and 197 characters.
Three changes fixed it:
- State the limit as a hard constraint in the system message, separately from the style guidance, and say what happens if it is exceeded — that over-length copy is worthless to the advertiser regardless of how well it reads.
- Repeat it inside the output schema, so the field the model is filling is labelled with its own ceiling.
- Ask for a self-check before emitting — count the characters and rewrite anything over.
With all three, the same model on the same product starts obeying. The lesson generalises past ad copy: a constraint mentioned in passing is treated as a preference, and one stated as a rule with a consequence is treated as a rule.
We still verify every variant afterwards and shorten the ones that overrun, because "starts obeying" is not "always obeys".
Writing to 30 characters without sounding like a telegram
The Google headline limit is the one people find brutal. Some things that help:
- Drop the article. "The best dashboard mat" → "Best dashboard mat" buys you four characters for free.
- Use the numeral. "Three" → "3".
- Cut the brand name unless it is the reason someone clicks. It is already displayed elsewhere in the ad.
- One idea per headline. You are supplying a pool of headlines that get assembled in combinations, not writing one sentence in three parts.
- Spend the characters on the specific thing. "360° rotation, no screws" uses 24 characters and says something. "Premium quality product" uses 23 and says nothing.
Do not write to the ceiling
Hitting exactly 40 is not the goal, and treating the limit as a target is its own mistake. A 26-character headline that says one concrete thing outperforms a 40-character one padded to the edge. The limit is a constraint to respect, not a quota to fill.
Frequently asked questions
What is the character limit for a Facebook ad headline?
40 characters. Primary text is best kept to 125 so it is not truncated behind "See more" on mobile, though the field itself accepts considerably more.
Are Instagram limits different from Facebook?
No — same 40 and 125, because they are bought through the same Meta ads system. The visual context differs, so the same copy can read very differently, but the counts are identical.
What is the TikTok ad caption limit?
40 for the headline and around 100 for the caption, and shorter is materially better because the text sits over the video.
Do emoji count as one character?
Not reliably. Many emoji are counted as two, and some flag and skin-tone variants as more. If you are close to a limit and using emoji, check in the platform's own editor rather than trusting a character count from elsewhere.
Do these limits change?
The Google ones have been stable for years. Meta adjusts what it truncates in the feed more often than it changes the field maximums, so treat 125 as a design target rather than a permanent number. We wrote up the Google Ads limits in detail separately.