TikTok ad caption rules: no links, @ or hashtags, and a 4-line limit

TikTok's auction in-feed ad page (read 2026-10-08) says non-Spark ad captions do not support clickable links, @ symbols or hashtags, and that Spark Ad captions are taken from the organic caption with a maximum of 4 lines. A few lines of Python can check your copy for those problems before you submit. Text burned into the video by Sume's captions route is picture content, not the ad caption field, so these rules apply to the caption text you type into the ad.

The rules on the page

The page lists the caption rules in two places, one for each ad type.

A lint to run first

This function flags links, @ symbols and hashtags, and counts lines. It has no network calls, so it runs as written.

import re

def lint_caption(text, spark=False):
    problems = []
    if re.search(r"https?://|www\.", text, re.I):
        problems.append("link")
    if "@" in text:
        problems.append("at sign")
    if "#" in text:
        problems.append("hashtag")
    if spark and len(text.splitlines()) > 4:
        problems.append("more than 4 lines")
    return problems

print(lint_caption("Shop now https://example.com #sale"))
print(lint_caption("Two line\ncaption", spark=True))

Where Sume fits

Sume's video captions route burns timed text into a finished clip at a public HTTPS URL, with a style, a language and optional script_text. The design block can move the caption line with placement.anchor_ratio, which the docs describe as the center of the line as a fraction of the frame height. That is separate from the ad caption field. If your burned-in words repeat a link or a hashtag, they are part of the picture and TikTok's caption rule does not describe them, so keep the lint for the field and check the page's safe-zone files for the picture. The size side of the same page is in this post.

Edge cases for the lint

The lint above is deliberately blunt. It flags any at sign or hash character, including one inside an email address or a number sign in a price list, because TikTok's page says the caption does not support @ symbols or hashtags and does not describe the exception cases. If your copy has a legitimate hash, rewrite it with a word instead of testing what TikTok does with it.

The line count assumes newline characters. A Spark Ad caption comes from the organic post, so count the lines as they appear in that post. Run the lint over every variant in a batch and fail the batch if any one has a problem. The function returns a list, so an empty list is a pass.

• Replace # with the word number or no.
• Replace @ in handles with the plain name.
• Keep a Spark caption to four lines or fewer.