How to fix media_unavailable for a public media URL in a social publishing API

Make the submitted imageUrl, videoUrl or everyimageUrls item reachable by MultiPost without cookies, browser login or private-network access. A 502 media_unavailable response means MultiPost could not fetch and host the supplied media.

Test the exact URL from a server-side environment, including redirects and expiry. A link that works only in your signed-in browser is not a public media input for an API publishing job.

Link the customer through MultiPost accounts, then send a stable HTTPS URL in the field matching the post type. MultiPost re-hosts external media on its verified storage before publishing to the selected networks.

API publishing is available on Pro and Agency. Check plans and billing separately from media reachability so a plan error is not misdiagnosed as a failed download.

Use imageUrl for an image, videoUrl for a video and one to twenty imageUrls for a slideshow. Text posts do not need media, while the target list must still contain at least one supported platform.

For a concrete multi-image payload, see how to schedule a TikTok photo slideshow from public image URLs.

Verify that the URL returns the intended file, remains valid long enough for processing, does not require custom browser headers and has not been replaced by an HTML error page. For a slideshow, test every item because one inaccessible source can invalidate media preparation.

Generate a new stable URL after fixing access and submit a deliberate new request. Do not loop on the same private or expired link; the response has already identified media preparation as the blocking stage.

MultiPost downloads and re-hosts the external file before the network publish or scheduled queue is accepted. Your integration remains responsible for supplying the correct asset and content type, while MultiPost handles the verified hosting step needed by supported targets.