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matrix-spec/content/rooms/v8.md

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---
title: Room Version 8
type: docs
weight: 60
---
This room version builds on [version 7](/rooms/v7) to introduce a new
join rule that allows members to join the room based on membership in
another room.
{{% boxes/warning %}}
This room version is known to have issues relating to redactions of member
join events. [Room version 9](/rooms/v9) should be preferred over v8 when
creating rooms.
{{% /boxes/warning %}}
## Client considerations
Clients are encouraged to expose the option for the join rule in their
user interface for supported room versions.
The new join rule, `restricted`, is described in the
[Client-Server API](/client-server-api/#restricted-rooms).
Clients which implement the redaction algorithm locally should refer to the
[redactions](#redactions) section below for a full overview.
### Redactions
{{% added-in this=true %}} `m.room.join_rules` events now keep `allow` in addition to other
keys in `content` when being redacted.
{{% boxes/warning %}}
[Room version 9](/rooms/v9) adds additional cases of protected properties for behaviour
related to restricted rooms (the functionality introduced in v8). v9 is preferred over
v8 when creating new rooms.
{{% /boxes/warning %}}
The full redaction algorithm follows.
Upon receipt of a redaction event, the server must strip off any keys
not in the following list:
- `event_id`
- `type`
- `room_id`
- `sender`
- `state_key`
- `content`
- `hashes`
- `signatures`
- `depth`
- `prev_events`
- `prev_state`
- `auth_events`
- `origin`
- `origin_server_ts`
- `membership`
The content object must also be stripped of all keys, unless it is one
of one of the following event types:
- `m.room.member` allows key `membership`.
- `m.room.create` allows key `creator`.
- `m.room.join_rules` allows keys `join_rule`, `allow`.
- `m.room.power_levels` allows keys `ban`, `events`, `events_default`,
`kick`, `redact`, `state_default`, `users`, `users_default`.
- `m.room.history_visibility` allows key `history_visibility`.
## Server implementation components
{{% boxes/warning %}}
The information contained in this section is strictly for server
implementors. Applications which use the Client-Server API are generally
unaffected by the intricacies contained here. The section above
regarding client considerations is the resource that Client-Server API
use cases should reference.
{{% /boxes/warning %}}
Room version 8 adds a new join rule to allow members of a room to join another
room without invite. Otherwise, the room version inherits all properties of
[Room version 7](/rooms/v7).
### Authorization rules
{{% added-in this=true %}} For checks performed upon `m.room.member` events, new
points for handling `content.join_authorised_via_users_server` are added (Rule 4.2
and 4.3.5).
{{% rver-fragment name="v8-auth-rules" %}}
### Redactions
[See above](#redactions).
## Unchanged from v7
The following sections have not been modified since v7, but are included for
completeness.
### Handling redactions
{{% rver-fragment name="v3-handling-redactions" %}}
### Event IDs
{{% rver-fragment name="v4-event-ids" %}}
### Event format
{{% rver-fragment name="v4-event-format" %}}
### State resolution
{{% rver-fragment name="v2-state-res" %}}
### Canonical JSON
{{% rver-fragment name="v6-canonical-json" %}}
### Signing key validity period
{{% rver-fragment name="v5-signing-requirements" %}}