---
type: module
weight: 50
---

### Fully read markers

The history for a given room may be split into three sections: messages
the user has read (or indicated they aren't interested in them),
messages the user might have read some but not others, and messages the
user hasn't seen yet. The "fully read marker" (also known as a "read
marker") marks the last event of the first section, whereas the user's
read receipt marks the last event of the second section.

#### Events

The user's fully read marker is kept as an event in the room's [account
data](#client-config). The event may be read to determine the user's
current fully read marker location in the room, and just like other
account data events the event will be pushed down the event stream when
updated.

The fully read marker is kept under an `m.fully_read` event. If the
event does not exist on the user's account data, the fully read marker
should be considered to be the user's read receipt location.

{{m\_fully\_read\_event}}

#### Client behaviour

The client cannot update fully read markers by directly modifying the
`m.fully_read` account data event. Instead, the client must make use of
the read markers API to change the values.

The read markers API can additionally update the user's read receipt
(`m.read`) location in the same operation as setting the fully read
marker location. This is because read receipts and read markers are
commonly updated at the same time, and therefore the client might wish
to save an extra HTTP call. Providing an `m.read` location performs the
same task as a request to `/receipt/m.read/$event:example.org`.

{{read\_markers\_cs\_http\_api}}

#### Server behaviour

The server MUST prevent clients from setting `m.fully_read` directly in
room account data. The server must additionally ensure that it treats
the presence of `m.read` in the `/read_markers` request the same as how
it would for a request to `/receipt/m.read/$event:example.org`.

Upon updating the `m.fully_read` event due to a request to
`/read_markers`, the server MUST send the updated account data event
through to the client via the event stream (eg: `/sync`), provided any
applicable filters are also satisfied.
