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Lemmy Nothing has to be registered before you start. Lemmy has no developer app, no client id and no redirect URI in this connector, and no key of yours goes into the .env file. You click Lemmy in Add Channel, a small form opens, and you type the three things your instance already knows about you.

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What she can post to Lemmy

A Lemmy post lives inside a community and carries a title of its own. Whatever you write in the editor becomes the body, the title comes from the post settings, and picking two communities sends the same body into both.

Character limit

10,000 characters in the body of the post.

Media

One image, sent as the cover of the post. She takes the first file attached and ignores the rest, and the file has to be a .png, a .jpg or a .gif.

Post types

A titled post in one community or several, then comments threaded under every one of them.

Analytics

None. Ten connectors report numbers back to her, and Lemmy is not one of them.
The media check looks for png, jpg or gif in the file path, and the fourth accepted spelling is jpef, which is a typo for jpeg. So a file ending in .jpeg is refused and comes back as “You can set only one picture for a cover”. Rename the file to .jpg and it goes through.

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Before you connect

An account with two factor authentication turned on cannot connect. The login call carries your name and your password and nothing else, so there is no second factor for her to send and Lemmy turns the request down.How that surfaces depends on your instance. She turns a rejection into “Invalid credentials” only when Lemmy answers with a 401, and some instances answer a missing second factor with a 400 instead. In that case the modal can close on a channel that looks connected and then fails on its first scheduled post. Either way the fix is the same: use an account without 2FA.
Two more things worth knowing before you type anything in:
  • Your password is used again on every publish. She does not keep a long-lived session. Each post, each comment and each community search logs in again with the credentials you saved. Change your Lemmy password later and the scheduled posts start failing without anyone telling you, so come back here and reconnect the channel whenever you rotate it.
  • The instance has to be reachable from the internet. The backend blocks requests that resolve to loopback, private or link-local addresses, so a Lemmy on localhost or on a private LAN address fails to connect. Self-hosters who run both sides on the same private network can set DISABLE_SSRF_PROTECTION=true, which is documented next to the setting in .env.example.

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Connect Lemmy

1

Open Add Channel and pick Lemmy

In PostQueen, click Add Channel and select Lemmy. A modal titled Add Provider opens with three fields, and there is no redirect out to the platform.
2

Fill in the three fields

Each label below is exactly what the modal shows you.
3

Press Connect

She signs in to your instance, reads your profile back and creates the channel with your display name and your avatar. If the sign-in fails you land back on the modal with “Invalid credentials”.
4

Pick a community when you write

Open the post editor, choose the Lemmy channel and click Add Community. Type a word into Search Community and she queries your instance for active communities that match, so the list you get is the one your instance returns.Choose a result and two more fields appear. Title is required and becomes the headline of the post. URL is optional and turns it into a link post. Add a second community and the same body goes out again with its own title.
The channel is in the left sidebar with its avatar and name. That is the whole confirmation: if it is in the list, she can post to it.

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Troubleshooting

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”Invalid credentials”

Three different causes end up behind the same message.
  1. The name or the password is wrong. Sign in to the instance in a browser with exactly the same pair.
  2. The account has two factor authentication turned on and your instance answered with a 401. The connector cannot answer a second factor at all, so see Before you connect for the case where the same account connects and then fails at publish time instead.
  3. Service points somewhere she cannot reach. Check the protocol, drop any trailing path, and confirm the host resolves publicly.

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Scheduled posts stopped going out and nothing changed in PostQueen

The Lemmy password changed. Every publish logs in again with the stored pair, so a rotated password breaks the channel from the platform side. Reconnect the channel with the new password.

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”You can set only one picture for a cover”

The first file attached to the post matches none of the accepted spellings. In practice it is a .jpeg file, because the accepted list carries jpef where jpeg was meant. Save the file as .jpg and attach it again.

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The instance is on your own network

Requests to loopback and private ranges are blocked before they leave the backend. Either publish the instance on a public hostname or set DISABLE_SSRF_PROTECTION=true on a deployment where both sides sit on a trusted private network.