You're building something that needs to post to social. The choice is between integrating each platform's native API yourself (15 OAuth flows, 15 rate-limit schemes, months of eng time) or using a unified social media posting API that handles all of them through one call. This guide covers both paths with real pricing, code examples, and platform-specific requirements so you can pick the right one and avoid the gotchas.
Table of contents
- What is a social media posting API?
- What can you do with a social media posting API?
- Unified vs. native: which do you need?
- How do I post to Instagram, TikTok, and LinkedIn from one API?
- How to post images and videos to multiple platforms via API
- Best unified social media posting APIs in 2026
- Social media posting API pricing compared
- Social media automation and scheduling API for developers
- Key takeaway
- FAQ
What is a social media posting API?
A social media posting API is a programmatic interface that lets your code publish content, like text, images, videos, carousels to social platforms without logging in manually. You send an HTTP request with your credentials and content; the API handles authentication, formatting, and delivery to the platform.
There are two types.
Native platform APIs are published directly by Instagram, X, TikTok, LinkedIn, and the others. They give you full feature access for that platform, but each one has its own OAuth flow, its own rate-limit logic, its own media spec requirements, and its own breaking-change cadence. You build one integration per platform.
Unified social media posting APIs (also called social media aggregator APIs) sit on top of all those native APIs and expose one consistent REST endpoint. You authenticate once with a bearer token. You POST to one URL. The unified layer handles format normalization, auth token management, retries, and media transcoding per platform. When TikTok or Instagram changes their API, the unified provider absorbs the update, so your integration doesn't break.
Most developers building multi-platform tools choose unified. The setup difference is hours vs. months.
What can you do with a social media posting API?
| Capability | What it does |
|---|---|
| Publish posts | Send text, images, videos, and carousels to one or multiple platforms in a single call |
| Schedule content | Queue posts for future publish times with a schedule_at timestamp, and no cron job required |
| Post to multiple platforms simultaneously | One request covers up to 15 platforms at once |
| Upload images and videos via API | Separate media endpoint returns a media ID; attach it to your post call |
| Post video to multiple platforms | Upload once; the API handles format and spec normalization per platform |
| Track post status | Poll for status or receive webhooks when posts go live, fail, or are delayed |
| Manage multiple accounts | Post on behalf of different connected accounts - standard for SaaS products and agencies |
| Pull analytics | Impressions, reach, and engagement data through the same bearer token, no second integration |
| Manage comments and DMs | Full engagement layer - read, reply, and moderate across platforms |
The last two matter more than most developers expect. Teams that start with posting almost always need comments and analytics within three months. With a unified API, those capabilities run on the same auth and the same endpoint structure. With native APIs, they're two more integration projects.
Unified vs. native: which do you need?
| Factor | Unified posting API | Native platform API |
|---|---|---|
| Platforms per integration | 10-15 at once | 1 |
| Setup time | Hours | Weeks per platform |
| Auth | Single bearer token | OAuth 2.0 per platform |
| Media normalization | Handled automatically | Your responsibility |
| Rate limit management | Managed by the provider | Your responsibility |
| Platform-specific features | 90%+ coverage for posting | 100% |
| Maintenance burden | On the provider | On your team |
| Breaking change response | Provider patches it | You patch it |
| Best for | Multi-platform tools, SaaS, AI agents | Deep ad tech, platform-specific automations |
The maintenance row is the one that surprises teams. Platform APIs change without much warning. When X restructured its API tiers in 2023, thousands of apps broke. When Meta updated Graph API permissions, apps that had skipped the new review process lost access overnight. If you're maintaining five separate platform integrations, every one of those changes is your problem. On a unified API, it's the provider's problem.
Go native when your product's core value depends on a single platform's specific features: TikTok Q&A replies, Instagram AR, LinkedIn's matched audiences at full depth. The access is worth the complexity.
Go unified when you're posting to more than two platforms, building for end-users who connect their own accounts, or shipping on a timeline. Instagram's Graph API OAuth setup alone takes weeks. Add TikTok, LinkedIn, and X and you're looking at months before writing a single feature for your actual product.
How do I post to Instagram, TikTok, and LinkedIn from one API?
With a unified posting API, you make one call and specify which platforms to target. Here's what that looks like with Zernio:
const { post } = await zernio.posts.createPost({
content: 'Cross-posting to all my accounts!',
scheduledFor: '2024-01-16T12:00:00',
timezone: 'America/New_York',
platforms: [
{ platform: 'twitter', accountId: 'acc_twitter123' },
{ platform: 'linkedin', accountId: 'acc_linkedin456' },
{ platform: 'bluesky', accountId: 'acc_bluesky789' }
]
});What makes this non-trivial to build natively is that each of those three platforms has completely different posting requirements. Here's what a unified API abstracts away for each.
Instagram Graph API automated posting requirements
To post to Instagram programmatically, the account must be a Business or Creator account linked to a Facebook Page. Personal Instagram accounts have no publishing API. The app must have the instagram_content_publish and pages_read_engagement permissions approved through Meta's app review.
Instagram enforces a limit of 25 API-published posts per Instagram account per 24 hours. Media must be submitted as a two-step process: first create a media container with the image URL or video URL, then publish the container. Instagram does not accept direct file uploads to the publishing endpoint, so the media must be at a publicly accessible URL before you can reference it. Stories and Reels have additional spec requirements (aspect ratio, duration) that differ from feed posts.
TikTok Content Posting API requirements
TikTok's Content Posting API is separate from the general developer platform and requires specific access approval. Apps need either the video.publish scope (for direct post, which publishes immediately) or the video.upload scope (which creates a draft the user can edit before publishing). Direct Post mode requires explicit approval from TikTok beyond standard developer access.
Unlike Instagram, TikTok uses a chunk-based upload flow for larger videos. Supported video length is 15 seconds to 60 minutes, with file size up to 4GB. The API accepts MP4 and WEBM formats.
LinkedIn API posting requirements
LinkedIn posting API distinguishes between posting to a personal profile and posting to a company/organization page. Personal profiles require the w_member_social permission. Company pages require w_organization_social. These are separate OAuth flows with separate approval requirements.
Character limits: 3,000 characters for company page posts, 3,000 for personal posts. LinkedIn's media upload is also a two-step process: initialize the upload, then upload the binary, then attach the asset ID to the post request. Video encoding requirements are stricter than most platforms (H.264, AAC audio, specific bitrate ranges).
All of this is what a unified social media aggregator API handles behind the scenes. You pass a single text string and a media file. The API takes care of the container creation, the encoding requirements, the permission differences, and the character limit enforcement per platform.
Stop building social integrations from scratch.
One API call to publish, schedule, and manage posts across 15+ platforms.
How to post images and videos to multiple platforms via API
Posting media is a two-step process on every major platform: upload first, then post. This keeps your post-creation calls lean and lets large files process separately.
Step 1: Upload the media file
curl -X POST "https://zernio.com/api/v1/media" \
-H "Authorization: Bearer sk_your_token" \
-F "file=@/path/to/video.mp4" \
-F "type=video"Step 2: Schedule the post with the media ID
Pass media_id in your post payload.
curl -X POST "https://zernio.com/api/v1/posts" \
-H "Authorization: Bearer sk_your_token" \
-H "Content-Type: application/json" \
-d '{
"scheduled_at": "2026-05-15T14:00:00Z",
"targets": [
{
"social_account_id": "sa_instagram_123",
"platform": "instagram",
"type": "reel"
},
{
"social_account_id": "sa_tiktok_456",
"platform": "tiktok",
"type": "video"
}
],
"text": "Caption for IG + TikTok",
"media": [
{ "media_id": "med_123" }
]
}'Media specs by platform
Understanding the limits per platform matters when you're validating content before sending it to the API.
| Platform | Max image size | Max video size | Supported video formats | Max video length |
|---|---|---|---|---|
| Instagram (Feed) | 8 MB | 4 GB | MP4, MOV | 60 minutes |
| Instagram (Reels) | N/A | 4 GB | MP4, MOV | 90 seconds |
| TikTok | N/A | 4 GB | MP4, WEBM | 60 minutes |
| 5 MB | 5 GB | MP4 (H.264) | 10 minutes | |
| X/Twitter | 5 MB | 512 MB | MP4, MOV | 2 minutes 20 seconds |
| 25 MB | 10 GB | MP4, MOV | 240 minutes | |
| YouTube | N/A | 256 GB | MP4, MOV, AVI | 12 hours (verified) |
Videos: Vertical (9:16) works best across TikTok, Instagram Reels, and YouTube Shorts. Square (1:1) performs well on Instagram Feed, Facebook, and LinkedIn. Zernio normalizes specs per platform by default. If you need per-platform overrides - say, a 16:9 version for LinkedIn and a 9:16 version for TikTok from the same source file - you can pass per-account content overrides in the payload.
Carousels: Upload each image separately, collect the media IDs, pass them as an array. Instagram supports 2-10 images. LinkedIn supports up to 20. Facebook supports up to 10. The API returns a validation error if you exceed the platform's limit.
Best unified social media posting APIs in 2026
This section covers unified posting APIs specifically: products that give you one endpoint for cross-platform publishing. For a comparison that also includes native platform APIs from Meta, X, TikTok, and LinkedIn, see the social media APIs for developers.
Feature comparison
| Feature | Zernio | Ayrshare | Upload-Post |
|---|---|---|---|
| Platforms | 15 | 13 | 11 |
| Posting API | ✓ | ✓ | ✓ |
| Scheduled posting | ✓ | ✓ | ✓ |
| Bulk scheduling | ✓ | ✓ | ✓ |
| Comments API | ✓ | ✓ | ✗ |
| DMs / messaging API | ✓ | ✗ | ✗ |
| Analytics API | ✓ | Limited | ✗ |
| Ads API | ✓ | ✗ | ✗ |
| Webhooks | ✓ | ✓ | Limited |
| MCP server (AI agents) | ✓ | ✗ | ✗ |
| White-label | ✓ | ✓ | ✓ |
| SOC 2 compliant | ✓ | ✓ | ✗ |
| Pricing model | Per account, volume discounts | Per profile | Per profile |
Zernio
15 platforms, the full social layer (posting, comments, DMs, analytics, ads), and pricing with volume discounts that drop as you grow. The MCP server gives AI agents 280+ tools for autonomous social publishing without custom wrappers - the only unified posting API with agent-native infrastructure.
Best for: SaaS platforms embedding social publishing, AI content tools, agencies managing multiple client accounts, AI agent builders who need autonomous social output.
Not ideal for: If you're a social media manager and you need a social posting tool from dashboard.
Ayrshare
Solid reliability, good documentation, broad platform coverage at 13 networks. Per-profile pricing means costs scale directly with your user count. No MCP server or agent tooling. At 100 connected accounts, approximately $900/month vs. Zernio's $318.
Best for: Teams evaluating unified posting APIs before deciding on a long-term architecture, projects with fewer than 20 connected accounts where per-profile pricing is still reasonable.
Not ideal for: SaaS products with growing end-user bases where per-profile pricing creates an unpredictable cost structure.
Upload-Post
Posting-focused unified API covering 11 platforms. Cheaper at very low account counts. No comments API, no DMs API, no analytics beyond basic post status.
Best for: Simple cross-platform publishing pipelines where engagement and analytics are handled elsewhere.
Not ideal for: Products that will eventually need the full social layer - you'll end up migrating.
Social media posting API pricing compared
| Accounts | Zernio | Ayrshare (est.) | Upload-Post (est.) |
|---|---|---|---|
| 10 | $48/mo | $299/mo | ~$39/mo |
| 50 | $168/mo | ~$778/mo | ~$105/mo |
| 100 | $318/mo | ~$1,230/mo | ~$172/mo |
| 500 | $718/mo | ~$2,620/mo | Custom |
| 2,000 | $2,218/mo | ~$6,400/mo | Custom |
Zernio is priced per account with volume discounts: accounts 3-10 at $6/month each, 11-100 at $3/month each, 101-2,000 at $1/month each. Every feature is included from account one - no add-ons, no tiers, no separate charge for analytics or DMs.
One note on X/Twitter: Zernio passes through X API costs at exact rates ($0.01/write, $0.005/read) with no markup. All other platforms are fully covered in the base price.
For the per-profile vs. flat-rate math in more detail, the Ayrshare vs. Zernio comparison has the full breakdown.
Social media automation and scheduling API for developers
Beyond single posts, three automation patterns come up most often in real developer integrations.
Scheduled publishing
Pass a schedule_at ISO 8601 timestamp and the API queues the post. No cron job, no background worker needed on your side. This is the foundation of any social media scheduling API integration - your app handles the content, Zernio handles the timing and delivery.
Use webhooks to get notified when scheduled posts go live or fail, instead of polling:
const zernio = new Zernio({ apiKey: process.env.ZERNIO_API_KEY });
const { data } = await zernio.webhooks.createWebhookSettings({
body: {
name: 'Example',
url: 'https://example.com',
events: [
'post.scheduled',
],
},
});
console.log(data);Programmatic content pipelines
Connect your content generation system (CMS, AI tool, database) to the posting API. When new content is ready, trigger a POST request. The API handles multi-platform delivery, retries on transient failures, and logs the result per platform. This is how AI-native tools like Vibiz and HeyMark use Zernio at scale: the LLM generates content, Zernio distributes it.
For analytics on top of your published content, the social media analytics API runs through the same bearer token. No second integration, no separate auth flow.
Key takeaway
A social media posting API cuts months of platform integration work down to an afternoon. Native APIs make sense when your automation needs platform-specific depth on one or two networks. For everything else - posting, scheduling, and automating across 10+ platforms - a unified API handles the infrastructure so you can build what actually matters.
The hidden cost isn't the API subscription. It's the engineering time for 15 separate OAuth flows, media specs, rate limit schemes, and the maintenance work every time a platform changes something. At any meaningful scale, that math points strongly toward unified.
Zernio covers 15 platforms, the full social layer, and agent-native tooling through one bearer token. Start building free - first 2 accounts included, no credit card required.
FAQ
What is a social media posting API?
A social media posting API is a programmatic interface that lets your application publish content to social platforms via HTTP requests. Instead of logging in manually, you send a structured request with your auth token, content, and target platforms, and the API handles delivery. Unified posting APIs like Zernio let you post to 15 platforms from one endpoint with a single bearer token.
Which tools offer automated social media posting via API?
The main unified options are Zernio (15 platforms, full social layer including comments, DMs, analytics, and ads), Ayrshare (13 platforms, per-profile pricing), and Upload-Post (11 platforms, posting-only). Native platform APIs from Meta, X, TikTok, and LinkedIn offer direct access to platform-specific features but require a separate integration per network. For the full comparison, see social media APIs for developers: 12 best options.
What is the difference between a unified social media API and a social media aggregator API?
They refer to the same category: a single REST endpoint that wraps multiple platform APIs. The unified layer normalizes authentication, media specs, rate limits, and response formats across all supported platforms so your code makes one call instead of 15.
How do I post to Instagram, TikTok, and LinkedIn from one API without managing each platform?
Use a unified social media posting API like Zernio. Connect your accounts once through OAuth, then specify the account IDs in a single POST request. The API handles format differences, media normalization, per-platform character limits, and publishing requirements automatically. Setup takes under an hour.
