Composer and media

Previews, limits and how each network counts

Every network counts text and media in its own way. 1Post checks each destination against its own rules before anything is queued and answers invalid_for_platform with the rule that failed. The post stays in your queue until you fix it, and no other destination is held back.

Also:The composer 1Post API error codes and how to fix each Social media posting limits by network

Updated 2026-10-26

What is checked

Text length by the network's own counting rule.
Image and video shape, size and count.
Features a network lacks, such as threads or polls.
Your plan's limits, such as the largest upload and how far ahead you can schedule.

Where to look up a rule

Each network has a specs and limits page with every text and media rule, its source and the date we read it. The posting limits table puts them side by side. The public tool platform_limits returns the same table over the API with no key.

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