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docs/admin/domain_permission_subscriptions.md

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+# Domain Permission Subscriptions
+
+Via the [admin settings panel](./settings.md#subscriptions), you can create and manage domain permission subscriptions.
+
+Domain permission subscriptions allow you to specify a URL at which a permission list is hosted. Every 24hrs at 11pm (by default), your instance will fetch and parse each subscribed list, and create domain permissions (or domain permission drafts) based on entries in the lists.
+
+## Limitations
+
+Currently, via blocklist subscriptions it is only possible to create "suspend" level domain blocks; other severities are not yet supported. Entries of severity "silence" or "limit" etc. on subscribed blocklists will be skipped.
+
+## Priority
+
+When you specify multiple domain permission subscriptions, they will be fetched and parsed in order of priority, from highest priority (255) to lowest priority (0).
+
+Permissions discovered on lists higher up in the priority ranking will override permissions on lists lower down in the priority ranking.
+
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+
+## Orphan Permissions
+
+aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+
+## Fun Stuff To Do With Domain Permission Subscriptions
+
+### 1. Create an allowlist-federation cluster.
+
+Domain permission subscriptions make it possible to easily create allowlist-federation clusters, ie., a group of instances can essentially form their own mini-fediverse, wherein each instance runs in [allowlist federation mode](./federation_modes.md#allowlist-federation-mode), and subscribes to a cooperatively-managed allowlist hosted somewhere.
+
+For example, instances `instance-a.example.org`, `instance-b.example.org`, and `instance-c.example.org` decide that they only want to federate with each other.
+
+Using some version management platform like GitHub, they host a plaintext-formatted allowlist at something like `https://raw.githubusercontent.com/our-cluster/allowlist/refs/heads/main/allows.txt`.
+
+The contents of the plaintext-formatted allowlist are as follows:
+
+```text
+instance-a.example.org
+instance-b.example.org
+instance-c.example.org
+```
+
+Each instance admin sets their federation mode to `allowlist`, and creates a subscription to create allows from `https://raw.githubusercontent.com/our-cluster/allowlist/refs/heads/main/allows.txt`, which results in domain allow entries being created for their own domain, and for each other domain in the cluster.
+
+At some point, someone from `instance-d.example.org` asks (out of band) whether they can be added to the cluster. The existing admins agree, and update their plaintext-formatted allowlist to read:
+
+```text
+instance-a.example.org
+instance-b.example.org
+instance-c.example.org
+instance-d.example.org
+```
+
+The next time each instance fetches the list, a new domain allow entry will be created for `instance-d.example.org`, and it will be able to federate with the other domains on the list.
+
+### 2. Cooperatively manage a blocklist.
+
+Domain permission subscriptions make it easy to collaborate on and subscribe to shared blocklists of domains that host illegal / fashy / otherwise undesired accounts and content.
+
+For example, the admins of instances `instance-e.example.org`, `instance-f.example.org`, and `instance-g.example.org` decide that they are tired of duplicating work by playing whack-a-mole with bad actors. To make their lives easier, they decide to collaborate on a shared blocklist.
+
+Using some version management platform like GitHub, they host a blocklist at something like `https://raw.githubusercontent.com/baddies/blocklist/refs/heads/main/blocks.csv`.
+
+When someone discovers a new domain hosting an instance they don't like, they can open a pull request or similar against the list, to add the questionable instance to the domain.
+
+For example, someone gets an unpleasant reply from a new instance `fashy-arseholes.example.org`. Using their collaboration tools, they propose adding `fashy-arseholes.example.org` to the blocklist. After some deliberation and discussion, the domain is added to the list.
+
+The next time each of `instance-e.example.org`, `instance-f.example.org`, and `instance-g.example.org` fetch the block list, a block entry will be created for ``fashy-arseholes.example.org``.
+
+### 3. Subscribe to a blocklist, but ignore some of it.
+
+Say that `instance-g.example.org` in the previous section decides that they agree with most of the collaboratively-curated blocklist, but they actually would like to keep federating with ``fashy-arseholes.example.org`` for some godforsaken reason.
+
+This can be done in one of two ways:
+
+1. The admin of `instance-g.example.org` creates an explicit domain allow entry for `fashy-arseholes.example.org` on their own instance. Because their instance is running in `blocklist` federation mode, [the explicit allow overrides the domain block entry](./federation_modes.md#in-blocklist-mode), and so the domain remains unblocked.
+2. Before the blocklist is re-fetched, the admin of `instance-g.example.org` creates a [domain permission exclude](./settings.md#excludes) entry for ``instance-g.example.org``. The domain ``instance-g.example.org`` then becomes exempt/excluded from automatic permission creation, and so the block for ``instance-g.example.org`` on the shared blocklist does not get created in the database of ``instance-g.example.org`` the next time the list is fetched.
+
+### 4. Subscribe directly to another instance's blocklist.
+
+Because GoToSocial is able to fetch and parse JSON-formatted lists of domain permissions, it is possible to subscribe directly to another instance's list of blocked domains via their `/api/v1/instance/domain_blocks` (Mastodon) or `/api/v1/instance/peers?filter=suspended` (GoToSocial) endpoint (if exposed).
+
+For example, the Mastodon instance `peepee.poopoo.example.org` exposes their block list publicly, and the owner of the GoToSocial instance `instance-h.example.org` decides they quite like the cut of the Mastodon moderator's jib. They create a domain permission subscription of type JSON, and set the URI to `https://peepee.poopoo.example.org/api/v1/instance/domain_blocks`. Every 24 hours, their instance will go fetch the blocklist JSON from the Mastodon instance, and create permissions based on entries discovered therein.
+
+## Example lists per content type
+
+Shown below are examples of the different permission list formats that GoToSocial is able to understand and parse.
+
+Each list contains three domains, `bumfaces.net`, `peepee.poopoo`, and `nothanks.com`.
+
+### CSV
+
+CSV lists use content type `text/csv`.
+
+Mastodon domain permission exports generally use this format.
+
+```csv
+#domain,#severity,#reject_media,#reject_reports,#public_comment,#obfuscate
+bumfaces.net,suspend,false,false,big jerks,false
+peepee.poopoo,suspend,false,false,harassment,false
+nothanks.com,suspend,false,false,,false
+```
+
+### JSON (application/json)
+
+JSON lists use content type `application/json`.
+
+```json
+[
+  {
+    "domain": "bumfaces.net",
+    "suspended_at": "2020-05-13T13:29:12.000Z",
+    "public_comment": "big jerks"
+  },
+  {
+    "domain": "peepee.poopoo",
+    "suspended_at": "2020-05-13T13:29:12.000Z",
+    "public_comment": "harassment"
+  },
+  {
+    "domain": "nothanks.com",
+    "suspended_at": "2020-05-13T13:29:12.000Z"
+  }
+]
+```
+
+### Plaintext (text/plain)
+
+Plaintext lists use content type `text/plain`.
+
+Note that it is not possible to include any fields like "obfuscate" or "public comment" in plaintext lists, as they are simply a newline-separated list of domains.
+
+```text
+bumfaces.net
+peepee.poopoo
+nothanks.com
+```