---
acl_categories:
- '@write'
- '@stream'
- '@fast'
arguments:
- display_text: key
  key_spec_index: 0
  name: key
  type: key
- display_text: group
  name: group
  type: string
- display_text: id
  multiple: true
  name: id
  type: string
arity: -4
categories:
- docs
- develop
- stack
- oss
- rs
- rc
- oss
- kubernetes
- clients
command_flags:
- write
- fast
complexity: O(1) for each message ID processed.
description: Returns the number of messages that were successfully acknowledged by
  the consumer group member of a stream.
group: stream
hidden: false
key_specs:
- RW: true
  begin_search:
    spec:
      index: 1
    type: index
  find_keys:
    spec:
      keystep: 1
      lastkey: 0
      limit: 0
    type: range
  update: true
linkTitle: XACK
railroad_diagram: /images/railroad/xack.svg
since: 5.0.0
summary: Returns the number of messages that were successfully acknowledged by the
  consumer group member of a stream.
syntax_fmt: XACK key group id [id ...]
title: XACK
---
The `XACK` command removes one or multiple messages from the
*Pending Entries List* (PEL) of a stream consumer group. A message is pending,
and as such stored inside the PEL, when it was delivered to some consumer,
normally as a side effect of calling [`XREADGROUP`]({{< relref "/commands/xreadgroup" >}}), or when a consumer took
ownership of a message calling [`XCLAIM`]({{< relref "/commands/xclaim" >}}). The pending message was delivered to
some consumer but the server is yet not sure it was processed at least once.
So new calls to [`XREADGROUP`]({{< relref "/commands/xreadgroup" >}}) to grab the messages history for a consumer
(for instance using an ID of 0), will return such message.
Similarly the pending message will be listed by the [`XPENDING`]({{< relref "/commands/xpending" >}}) command,
that inspects the PEL.

Once a consumer *successfully* processes a message, it should call `XACK`
so that such message does not get processed again, and as a side effect,
the PEL entry about this message is also purged, releasing memory from the
Redis server.

## Examples

```
redis> XACK mystream mygroup 1526569495631-0
(integer) 1
```

## Redis Software and Redis Cloud compatibility

| Redis<br />Software | Redis<br />Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> |
|:----------------------|:-----------------|:------|
| <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> |  |

## Return information

{{< multitabs id="xack-return-info" 
    tab1="RESP2" 
    tab2="RESP3" >}}

[Integer reply](../../develop/reference/protocol-spec#integers): The command returns the number of messages successfully acknowledged. Certain message IDs may no longer be part of the PEL (for example because they have already been acknowledged), and XACK will not count them as successfully acknowledged.

-tab-sep-

[Integer reply](../../develop/reference/protocol-spec#integers): The command returns the number of messages successfully acknowledged. Certain message IDs may no longer be part of the PEL (for example because they have already been acknowledged), and XACK will not count them as successfully acknowledged.

{{< /multitabs >}}