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Destination · publishing reference

# Facebook Reels publishing reference for Postdom

This Facebook Reels publishing reference explains the configured Reel path, account connection, enforced limits, sent settings, and result boundary.

[Create a workspace](https://app.postdom.com/signup) [Read publish_video](https://postdom.com/docs/tools/publish-video)

Human authorization boundary

## Facebook Reels publishing reference connection requirements

A human completes the destination connection. The agent receives the resulting account ID—not the social credential—and supplies that exact account ID to `publish_video`.

`connection`

OAuth

`prerequisite`

No additional Postdom prerequisite is recorded beyond an eligible account.

`current source surface`

reel, feed, story

Configured output

## What Postdom sends to Facebook Reels

The public tool accepts product-level publishing fields. Postdom builds destination settings after validation; callers cannot smuggle an undocumented settings object through `publish_video`.

**`surface.facebook`** — **omitted (default) or reel | feed | story (current source)**  An omitted surface uses the media-dependent default; video defaults to Reel. This input exists in current source and is separate from released @postdom/mcp@0.4.0.

**`contentType`** — **reel**  Default video output. Current source omits contentType for feed and sends story for Story.

**`visibility`** — **omitted**  Postdom sends no Facebook audience setting; the connected account controls it.

This example is the default video path, not the only current-source path. The released @postdom/mcp@0.4.0 helper maps Facebook video to Reel and exposes no surface override. Current source also accepts surface.facebook as reel, feed, or story and translates that choice for the provider. Neither contract sends a Facebook visibility setting; account-side audience controls remain outside the tool schema.

_CURRENT SOURCE ADAPTER OUTPUT · NOT TOOL INPUT_

```
{
  "platform": "facebook",
  "settings": {
    "contentType": "reel"
  }
}
```

Enforced, documented, or unknown

## Facebook Reels publishing limits

Every row comes from the current `@postdom/core` registry. “Postdom enforced” means the source contract checks the fact. A recommendation, documented-but-unenforced fact, or unpublished value must not be presented as a passed validation.

 Postdom enforced

### caption max chars

**4000**

Postdom contract · verified 2026-08-21T00:00:00.000Z

Evidence reference retained in the core registry.

 Postdom enforced

### media max bytes

**524,288,000 bytes**

Postdom contract · verified 2026-08-21T00:00:00.000Z

Evidence reference retained in the core registry.

 Postdom enforced

### video max seconds

**600**

Postdom contract · verified 2026-08-21T00:00:00.000Z

Evidence reference retained in the core registry.

 Postdom enforced

### video mime types

**video/mp4, video/quicktime**

Postdom contract · verified 2026-08-21T00:00:00.000Z

Evidence reference retained in the core registry.

 Postdom enforced

### image mime types

**image/jpeg, image/png, image/gif, image/webp**

Postdom contract · verified 2026-08-21T00:00:00.000Z

Evidence reference retained in the core registry.

 Not published

### reels publishing description

**Not published**

Unit: not stated · Field: description · Scope: POST /{page-id}/video_reels

Platform evidence · verified 2026-09-03T00:00:00.000Z

Qualification

Meta publishes no maximum for this field, so there is no number to enforce.

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Postdom enforced

### video min seconds

**3**

Platform evidence · verified 2026-09-02T00:00:00.000Z

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Postdom enforced

### video max seconds

**90**

Platform evidence · verified 2026-09-02T00:00:00.000Z

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Recommendation

### video mime types

**video/mp4**

Platform evidence · verified 2026-09-02T00:00:00.000Z

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Not published

### resolution max pixels

**Not published**

Platform evidence · verified 2026-09-02T00:00:00.000Z

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Recommendation

### resolution recommended

**width: 1080; height: 1920**

Platform evidence · verified 2026-09-02T00:00:00.000Z

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Recommendation

### aspect ratio recommended

**9:16**

Platform evidence · verified 2026-09-02T00:00:00.000Z

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Documented, not enforced

### resolution min pixels

**width: 540; height: 960**

Platform evidence · verified 2026-09-02T00:00:00.000Z

Qualification

Meta's own floor - "Minimum is 540 x 960 pixels" - and the first Facebook resolution fact we hold from Meta rather than from the provider, which published none. Not gated because gating it would add a rejection, and this whole re-sourcing exists because Postdom was rejecting Reels Meta accepts. A floor read off one documentation line can be wrong in the direction that costs a customer a post, so it is recorded and left unread until a request is observed failing on it.

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

 Documented, not enforced

### aspect ratio

**minimum: 0.5625; maximum: 1.7777777777777777**

Platform evidence · verified 2026-09-02T00:00:00.000Z

Qualification

"Aspect ratios for videos need to be between 16x9 and 9x16", from error code 1363040 rather than from the specification table. Taken from the error table deliberately: the spec table lists "9 x 16" as the target, while the error table states what Meta actually rejects, and a rejection contract is the stronger evidence of a bound. The two do not conflict - 9:16 sits at one end of the published range. Recorded as the range rather than the target so a square video is not read as violating a limit Meta does not impose. Not gated: the Facebook preflight branch reads durations only.

[Official source](https://developers.facebook.com/docs/video-api/guides/reels-publishing)

Result boundary

## How to verify the Facebook Reels outcome

This page describes the current source contract. It does not claim an authenticated Page Reels publication test or guarantee that every platform field is observable.

### Never collapse a workflow state into success

Store the Postdom post ID, read the exact destination state with `get_publish`, and preserve a missing public URL, approval state, terminal refusal, or provider error exactly as returned.

Nine modeled fields

## Facebook Reels metric availability

The matrix records evidence states, not guaranteed live values. Unverified and never remain null with a reason; zero remains a measured zero.

| Metric | State | Baseline | Value behavior |
| --- | --- | --- | --- |
| views Views Required view count in a normalized snapshot. | available | 2026-09-02T00:00:00.000Z | Numeric when a snapshot exists. Zero remains zero. |
| likes Likes Required like count in a normalized snapshot. | available | 2026-09-02T00:00:00.000Z | Numeric when a snapshot exists. Zero remains zero. |
| comments Comments Required comment count in a normalized snapshot. | available | 2026-09-02T00:00:00.000Z | Numeric when a snapshot exists. Zero remains zero. |
| shares Shares Required share count in a normalized snapshot. | available | 2026-09-02T00:00:00.000Z | Numeric when a snapshot exists. Zero remains zero. |
| saves Saves Nullable saved or favorited count. | unverified | Not verified | Always null with an explicit reason. |
| watch_time_s Watch time Nullable total watch time in seconds. | unverified | Not verified | Always null with an explicit reason. |
| avg_watch_pct Average watch Nullable average watched percentage. | unverified | Not verified | Always null with an explicit reason. |
| completion_pct Completion Nullable completion percentage. | unverified | Not verified | Always null with an explicit reason. |
| follower_delta Follower delta Nullable follower-change field. | estimable | 2026-09-02T00:00:00.000Z | Currently normalized to null; derivation is not promised. |

Separate search intent

## Related Facebook Reels resources

These pages answer separate workflow, specification, or character-limit questions. They support this product reference without replacing it.

### Facebook Reels video requirements

Search-focused requirements research and source context.

[Open resource](https://postdom.com/platforms/facebook-reels/video-requirements)

Verification scope

## Facebook Reels evidence boundary

### Contract evidence is not an observed publication

These pages describe source-backed product contracts. They do not represent an authenticated end-to-end publication or analytics test.

Inspect the connected tool schema before acting. Current source may be ahead of the separately published `@postdom/mcp` helper.

Use the contract

## Publish with explicit authority and outcomes

Create a workspace, connect an eligible account, and let the agent use only the fields exposed by the connected schema.

[Start free](https://app.postdom.com/signup) [Read outcome states](https://postdom.com/docs/tools/get-publish)

 VERIFIED · 23 SEPTEMBER 2026  **Current source adapter · Core evidence registries · Modeled metric availability**

Private identifiers and unverified publication claims are excluded. External links are limited to first-party platform sources.