# What is the QoS parameter of the mqtt in node?

**URL:** <https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896>\
**Category:** General\
**Created:** [29 August 2023 23:38 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896 "2023-08-29T23:38:47Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![AndreKR](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/andrekr/32/81657_2.png) [@AndreKR](https://discourse.nodered.org/u/AndreKR)\
**Post date:** [29 August 2023 23:38 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/1 "2023-08-29T23:38:48Z")

</div>

I don't understand the meaning of the QoS parameter in the _mqtt in_ node. Is it some kind of filter?

---

<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [30 August 2023 00:12 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/2 "2023-08-30T00:12:55Z")

</div>

This is generally considered the best explanation: [What is MQTT Quality of Service (QoS) 0,1, & 2? – MQTT Essentials: Part 6 (hivemq.com)](https://www.hivemq.com/blog/mqtt-essentials-part-6-mqtt-quality-of-service-levels/).

---

<div class="post-metadata">

**Author:** ![AndreKR](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/andrekr/32/81657_2.png) [@AndreKR](https://discourse.nodered.org/u/AndreKR)\
**Post date:** [30 August 2023 00:44 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/3 "2023-08-30T00:44:31Z")

</div>

I'm not asking what the QoS values mean, I understand what they mean when _publishing_ messages.

I'm asking what the purpose of setting a QoS is when _receiving_ messages.

---

<div class="post-metadata">

**Author:** ![AndreKR](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/andrekr/32/81657_2.png) [@AndreKR](https://discourse.nodered.org/u/AndreKR)\
**Post date:** [30 August 2023 00:45 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/4 "2023-08-30T00:45:50Z")

</div>

Oooh, that's the QoS of the subscription, right?

---

<div class="post-metadata">

**Author:** ![kuema](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kuema/32/6542_2.png) [@kuema](https://discourse.nodered.org/u/kuema)\
**Post date:** [30 August 2023 04:26 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/5 "2023-08-30T04:26:39Z")

</div>

Yes, QoS levels of publishers and subscribers _can_ be different, which _could_ have effects on message delivery.

For reference, search for the paragraph "Downgrade of QoS" in the link provided above.

---

<div class="post-metadata">

**Author:** ![cymplecy](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cymplecy/32/2773_2.png) [@cymplecy](https://discourse.nodered.org/u/cymplecy)\
**Post date:** [30 August 2023 07:12 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/6 "2023-08-30T07:12:49Z")

</div>

The subscription QoS will be ignored if it's higher than one published to the broker according to spec

If it's lower than the published one , then it will be obeyed

e.g pub as 0, sub as 2 - broker will use 0 - pub as 2, sub as 1, broker will use 1

But the mosquito broker can be (mis) configured to not do this 🙂

> **[MQTT QoS level between publisher and subscribers](https://blog.famzah.net/2022/10/03/mqtt-qos-level-between-publisher-and-subscribers/)**
>
> MQTT QoS level upgrade/downgrade between publisher and subscribers

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [29 October 2023 07:13 UTC](https://discourse.nodered.org/t/what-is-the-qos-parameter-of-the-mqtt-in-node/80896/7 "2023-10-29T07:13:04Z")

</div>

This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.