Social Media Character Limits per Platform

Caption limits per platform

The caption field is the one people hit first. Threads is the strictest at 500 characters, which is why a campaign caption often needs a Threads-specific version. Instagram and TikTok share a 2200-character ceiling, and Facebook allows 4000 per post. A YouTube upload is different: the content field is the video description, capped at 5000 bytes, and the title is a separate field with a 100-character limit.

Thread and sequence limits

Threads is the only platform here that ships linked sequences, and it has two ceilings that apply at the same time. A single text post carries up to 500 characters, and a thread sequence holds up to 10 items with a separate 500-character budget for each item. Every item also counts toward the account rate limit of 250 posts per user per 24 hours, so a 10-item thread consumes ten of that budget.

• Text post: 500 characters.
• Thread item: 500 characters each, up to 10 items per sequence.
• Daily cap: 250 posts per user per 24 hours, counting each item.

Carousel and media limits

Media caps differ more than captions do. Instagram carousels stop at 10 photo items and cannot mix stills with video. TikTok photo carousels take up to 35 images. YouTube accepts video only. No platform in the workflow accepts a mixed photo and video payload, so each request stays either photo-based or video-based.

Shared video profile

Video follows one profile across the platforms that accept it: MP4 or MOV container, H.264 codec recommended, 9:16 vertical at 1080x1920 for short-form feeds, and a duration between 3 seconds and 10 minutes for TikTok. Preparing media to that profile once means the same file can be published to several platforms without re-encoding, which is the point of running them through one endpoint.

Where these limits are enforced

The publishing endpoint validates the caption length, the media type, and the per-platform caps before the request is queued. A caption that is too long, a carousel with 11 images, or a payload that mixes photos with video fails with a 400 and a message naming the rule. Nothing is charged against the monthly upload quota for a rejected request, and nothing reaches the platform, so a validation failure costs a fix rather than a publish credit. The per-platform pages and the media guides go deeper on each rule.