BlogPlatform rules and limits
DM automation API: what each social platform lets you build
Two jobs share the name. Comment to DM messages whoever commented a keyword. Auto-reply answers people who messaged you first. The platforms decide which one you can build, not the tools.
The short answer
Only Instagram and Facebook let an app send a DM in reply to a public comment: one message per comment, within 7 days. Instagram, Facebook, WhatsApp, X, Telegram, Bluesky and TikTok (in beta) let apps answer DMs people send first. Only X and Bluesky let an app message someone first, and LinkedIn, YouTube and Threads have no open DM API at all.
Facts as of November 2, 2026
Platform by platform
| Platform | Comment to DM | Answer inbound DMs | Message first | What you need |
|---|---|---|---|---|
| Yes: one private reply per comment, within 7 days | Yes, within 24 hours of their last message | No | Professional account; App Review and Business Verification for accounts you don't own | |
| Facebook (Messenger) | Yes: one private reply per Page comment, within 7 days | Yes, within 24 hours; tags outside it, never for promotions | No, except paid sponsored messages and opted-in notifications | A Page and the pages_messaging permission |
| No (no public comments) | Yes, within a 24-hour customer service window | Only pre-approved templates, to people who opted in | WhatsApp Business Platform | |
| X | No built-in feature; an app can DM a replier through the DM endpoint | Yes | Yes, unless the person's settings block DMs from people they don't follow | Pay-per-use API with user sign-in; per-user daily limits |
| Telegram | No | Yes | No: "Bots can't start conversations with users." | Free bot token |
| Bluesky | No built-in feature; an app can DM a replier | Yes | Yes, if the person allows DMs from everyone | Free; an app password with DM access |
| TikTok | Not found | Yes, through the Business Messaging API | Not found in TikTok's docs | Open beta in some regions, not the EEA, Switzerland or the UK; verified business accounts |
| No | Approved partners only, and only on a member's own action | No | Partner agreement | |
| YouTube | No (comment replies only) | No DM API | No | None for DMs |
| Threads | No | No DM endpoints found | No | None for DMs |
Read on each platform's own developer pages, November 2, 2026. "Not found" means we looked and the docs do not say.
SourcesMeta for Developers: Private RepliesMeta for Developers: Messenger private repliesMeta for Developers: WhatsApp Cloud API, send messagesX API docs: Direct MessagesTelegram Bot APIAT Protocol chat lexiconsTikTok Business Messaging APILinkedIn Messages APIYouTube Data API: comments.insertThreads API: reply management
Why comment to DM is a Meta thing
Meta built private replies on purpose: someone comments, and the business may answer once, in private. Instagram and Facebook are the only platforms with that endpoint. On X and Bluesky an app can DM anyone who allows it, so a comment trigger is something the tool builds itself, and on the rest there is no route at all.
On Instagram it comes with limits: 750 private replies an hour per account, one per comment, and follow-ups only after the person answers. Every limit is in our post on Instagram DM limits.
Nobody can cold DM on Instagram
"Conversations only begin when an Instagram user sends a message to your app user." That rule is the same for every tool, ours included. A tool that offers to DM people who never wrote or commented cannot be doing it through the official API.
Build it yourself, or use a tool
Building on Instagram's API means a Meta app, App Review, Business Verification for accounts you don't own, webhooks for comments and messages, the 24-hour window, and token refresh. A tool has done that once for everyone. What it should hand you is an API of its own, so your code or your AI agent can still build on top.
Postkey has a REST API (postkey.pro/docs/api) and an MCP server: AI assistants use the MCP server, and scripts, n8n and Make can use either. DM automations run on Instagram and Messenger today.
That is why Postkey is the most agentic DM automation tool: the same automations you build by hand, an agent can build, edit and switch on, with your yes before anything goes live.
Questions
Is there an API for Instagram DM automation?
Yes. Meta's Instagram API has private replies (comment to DM) and a Send API for conversations people start. You need an Instagram professional account and, for accounts you don't own, App Review.
Can an API send Instagram DMs to people who never messaged me?
No. On Instagram a conversation starts with the person: a DM, a comment, a story reply or an ad click.
Does TikTok have a DM automation API?
TikTok's Business Messaging API is in open beta in some regions for verified business accounts, for answering people who message first. We found no comment-to-DM in its docs.
Can I automate LinkedIn DMs?
Not through an open API. LinkedIn's messaging API is for approved partners, and each message has to follow a member's own action.
Is there a DM automation API I can use without building a Meta app?
Yes. Postkey has a REST API and an MCP server on top of Meta's official API, for Instagram and Messenger DM automations, so your code or your AI agent builds on it without App Review.
