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Substack file embeds
substack.comMediastorage/substack-file-embedsJSONcomparereport an errorprovider JSON
- Free allowance
- No stated total; 700 MB per PDF, XLSX/CBZ/CBR embeds supported
- Verdict
- caveatusable, with a named limit or an unprobed read path
- Cost
- free tier
- Identity
- institution?placeholder, not evidence; card unknown, phone unknown
- Binding limit
- noneno named constraint binds
- Evidence
- reported2 sources; a third party said so
- Freshness
- stale on 2026-11-05checked 2026-10-21 (inherited); stale on 2026-11-05
| Free tier | no stated total; 700 MB per PDF, XLSX/CBZ/CBR embeds supported unit MB; metered on unstated |
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| Price | none stated |
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| Identity | institution (inferred, not read) not published |
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| Egress | free, CDN-served download links on substackcdn.com, no auth for public posts |
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| Per-object cap | not stated |
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| Retention | not stated |
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| Interface | unknown wrapper-only |
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| Tooling | no public upload API — file embeds are drag-and-drop in the post editor or into email drafts; would need browser automation (Playwright) against the logged-in editor |
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| Composes with | 700 MB x unlimited posts x unlimited publications (each free to create). This is the largest per-file limit of any social platform checked here; 20 TiB = ~29,000 PDFs |
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| Reliability | attachments live with the post; editing a post can drop the embed; Substack has no delete-then-restore story. No API is the hard blocker — this is a 'if someone writes the Playwright wrapper' candidate |
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| Parsed numbers | |
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Evidence 2
Unknown values 5
- interface: the access interface was not established
- per object cap notes: the field may be stated in a source that was not read
- per object cap stated: the field may be stated in a source that was not read
- retention notes: the field may be stated in a source that was not read
- retention stated: the field may be stated in a source that was not read