matrix-spec/content/rooms/v8.md

---
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" %}}