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documentation/content/en/spec/webfinger.md
trwnh 3628b6d434
Update content for 4.0 (part 1) (#991)
* add rules

* join date on profiles

* deprecate follow scope

* deprecate identity proofs

* familiar followers

* use definition lists instead of tables for defining activitypub properties

* reformat notifications page into markdown

* fix broken links to publicKey header

* Application website is now nullable

* update environment variables added and removed

* fix typo

* fix heading level

* min_id and max_id can be used at the same time (3.3)

* fix typo

* new tootctl options

* reformat tootctl page to use definition lists for params

* add rules and configuration to Instance

* fix typo

* refactor instance api page

* 3.3.0 duration on mutes

* 3.3.0 mute_expires_at

* improve section headings

* 3.4.0 resend email confirmation api

* 3.4.0 policy on push subscriptions

* 3.4.0 add details to account registration error

* refactor accounts api page and start adding relrefs to entity pages

* 3.4.0 accounts/lookup api

* add see also to accounts methods

* add more see-also links

* 3.5.0 appeal mod decisions

* 3.5.0 reformat reports and add category/rule_ids params

* document report entity and missing responses

* fix typos

* fix relrefs and url schema, add aliases to old urls

* add archetypes for new methods/entities

* update archetypes with see-also stubs

* clearer presentation of rate limits

* announcements api methods

* refactor apps methods

* refactor bookmarks methods + some anchors

* refactor conversations methods

* custom_emojis methods refactor

* anchors

* refactor directory methods

* refactor domain_blocks methods

* add see also to emails methods

* fix page relref shortcodes to specific methods + refactor endorsements methods

* min_id max_id

* refactor favourites methods

* refactor featured_tags methods

* refactor filters methods, make path params consistent, i18n required shortcode

* follow_requests methods

* lists methods

* markers methods

* forgot to add entity links

* media methods, also fix formatting of some json errors

* mutes methods, add more see-also links

* oembed methods

* preferences methods

* proofs methods

* push methods

* suggestions methods

* 3.5.0 add new trend types, fix formatting

* refactor streaming methods

* refactor oauth methods

* note that streaming api casts payload to string

* refactor search methods

* refactor polls methods

* remove unnecessary link

* reformat scheduled_statuses methods

* reformat timelines methods

* reformat statuses methods

* 3.5.0 editing statuses

* consistent use of array brackets in form data parameters

* update dev setup guide, add vagrant and clean up text

* add admin/accounts methods

* 3.6 role entity

* admin/accounts methods v2

* minor fix

* stub admin/reports methods

* document admin reports

* add 403 example to methods archetype

* cleanup entities for admin reports and add new attrs

* 3.6.0 domain allows methods + normalize admin entity namespace

* fix search-and-replace error

* add aliases for admin entities

* 3.6.0 canonical email blocks entity

* 3.5.0 admin/retention api

* 3.5.0 add admin::ip doc

* 3.5.0 admin/reports

* 3.6.0 admin/domain_allows

* 3.5.0 admin/dimensions

* 3.6.0 permissions and roles

* minor formatting fix

* add anchor link to headings

* checkpoint

* add update commands to dev env setup guide

* change mentions of v3.6 to v4.0

* tootctl now uses custom roles

* fix formatting

* v2 instance api

* update frontmatter, add better titles to pages

* minor wording change

* consistency

* add more aliases

* add placeholders and WIP notices

* explain link pagination and stub out todos

* switch baseURL to https

* 422 on reports with rules but category!=violation

* document bug fixes

* fix typo

* remove duplicate API method definition

* s/tootsuite/mastodon for github links

* remove unnecessary escaping

* s/tootsuite/mastodon in Entity archetype

* add missing nullable shortcode

* clarify oauth scope when requesting a user token

* api/v2/media now synchronous for images

* DISALLOW_UNAUTHENTICATED_API_ACCESS

* add undocumented env variables

* add instance domain blocks and extended description api

* add SMTP_ENABLE_STARTTLS

* add description to SMTP_ENABLE_STARTTLS

* take suggestions from open PRs

* normalize links and flavour language

* Fully document streaming API based on source code

* Add mention of MIME types

* bump to ruby 3.0.4

* clarify how to check on async media processing

* validation of replies_policy

* remove TODOs on admin account action

* EmailDomainBlocks

* IpBlocks

* Admin::DomainBlock

* remove TODOs

* following hashtags

* followed_tags

* remove reference to unused parameter

* add new oauth scopes for admin blocks and allows

* fix command signature for i18n-tasks normalize

* reformat code structure page

* document fixes for following tags (assume 4.0.3)

* Add warning about pre-4.0 hardcoded roles

* add note about case sensitivity

* remove use of 'simply' from docs

* remove reference to silencing

* add reference to IDN normalization for verified links

* add lang parameter
2022-11-20 07:34:38 +01:00

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Markdown

---
title: WebFinger
description: Translate `user@domain` mentions to actor profile URIs.
menu:
docs:
weight: 20
parent: spec
---
## What is WebFinger, and why is it used? {#intro}
On Mastodon, user profiles can be hosted either locally on the same website as yours, or remotely on a completely different website. The same username may be used on a different domain. Therefore, a Mastodon user's full mention consists of both the username and the domain, in the form `@username@domain`. In practical terms, `@user@example.com` is not the same as `@user@example.org`. If the domain is not included, Mastodon will try to find a local user named `@username`. However, in order to deliver to someone over ActivityPub, the `@username@domain` mention is not enough -- **mentions must be translated to an HTTPS URI first**, so that the remote actor's inbox and outbox can be found.
Enter WebFinger. WebFinger as described in [RFC 7033](https://tools.ietf.org/html/rfc7033) is a spec that defines **a method for resolving links to a resource**, given only a URI on a particular server. This allows anyone to look up where a resource is located without having to know its exact location beforehand; for example, by email or phone number. This lookup is directed at the endpoint `/.well-known/webfinger`, and a `resource` query parameter is passed along with the lookup. The resource URI used with Mastodon is the `acct:` URI as described in [RFC 7565](https://tools.ietf.org/html/rfc7565), with the username of a profile that is hosted on a particular domain.
{{< hint style="danger" >}}
**Because Mastodon heavily relies on mentions for addressing other profiles, WebFinger is required for fully interoperating with Mastodon.** Users can generally load profiles by searching for the direct HTTPS URI if they know it, or for the `username@domain` address, but Mastodon's internal logic depends almost completely on `acct`: URIs or `username@domain` representations. Searching for any objects or profiles from an ActivityPub implementation without WebFinger will fail because the author cannot be converted to a user in the local database.
{{< /hint >}}
## Sample WebFinger flow {#example}
Suppose we want to lookup the user `@Gargron` hosted on the `mastodon.social` website.
Just make a request to that domain's `/.well-known/webfinger` endpoint, with the `resource` query parameter set to an `acct:` URI.
{{< code title="https://mastodon.social/.well-known/webfinger?resource=acct:gargron@mastodon.social" >}}
```json
{
"subject": "acct:Gargron@mastodon.social",
"aliases": [
"https://mastodon.social/@Gargron",
"https://mastodon.social/users/Gargron"
],
"links": [
{
"rel": "http://webfinger.net/rel/profile-page",
"type": "text/html",
"href": "https://mastodon.social/@Gargron"
},
{
"rel": "self",
"type": "application/activity+json",
"href": "https://mastodon.social/users/Gargron"
},
{
"rel": "http://ostatus.org/schema/1.0/subscribe",
"template": "https://mastodon.social/authorize_interaction?uri={uri}"
}
]
}
```
{{< /code >}}
You can parse this JSON response to find a link with your desired type. For ActivityPub `id`, we are interested in finding `application/activity+json` specifically.
This way, we have translated `@Gargron@mastodon.social` to `https://mastodon.social/users/Gargron` and we can now interact over ActivityPub by referring to this URI as `id` where appropriate.
{{< code title="Sample activity" >}}
```json
{
"id": "https://social.example/activities/1",
"type": "Create",
"actor": "https://social.example/actors/1",
"object": {
"id": "https://social.example/objects/1",
"type": "Note",
"content": "Hello, Gargron!"
},
"to": "https://mastodon.social/users/Gargron"
}
```
{{< /code >}}
Note in the above example that `social.example` does not use the same URI structure as Mastodon. Thus, we cannot guess the actor `id` given only the username and domain. However, if `social.example` supports WebFinger, then we can get this `id` by requesting `https://social.example/.well-known/webfinger?resource=acct:username@social.example`and parsing the response for a link with the `application/activity+json` type.