Unduplicator listing (#3633)

* Unduplicator listing

* Update contents/apps/unduplicator/docs.md

Co-authored-by: Andy Vandervell <92976667+andyvan-ph@users.noreply.github.com>

* Update contents/apps/unduplicator/docs.md

Co-authored-by: Andy Vandervell <92976667+andyvan-ph@users.noreply.github.com>

Co-authored-by: Andy Vandervell <92976667+andyvan-ph@users.noreply.github.com>

contents/apps/unduplicator/docs.md

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+---
+title: Unduplicator documentation
+showTitle: true
+topics:
+    - unduplicator
+---
+
+### What does the Unduplicator do?
+
+This app prevents duplicate events from being ingested into PostHog. It's particularly helpful if you're backfilling information while you're already ingesting ongoing events. 
+
+### How does the Unduplicator work?
+
+The Unduplicator crafts an event UUID based on key properties for the event, so if the event is the same (see below for definition) it'll end with the same UUID.
+
+When events are processed by ClickHouse, the database will automatically dedupe events which have the same `toDate(timestamp)`, `event`, `distinct_id` and `uuid` combo, effectively making sure duplicates are not stored.
+
+The app has two modes that define what's considered a duplicate event. Either mode will prevent duplicates within a project, though duplicates across projects are still permitted.
+
+- **Event and Timestamp**. An event will be treated as duplicate if the timestamp, event name and user's distinct ID matches exactly, regardless of what internal properties are included.
+- **All Properties**. An event will be treated as duplicate only if all properties match exactly, as well as the timestamp, event name and user's distinct ID.
+
+### What are the requirements for this app?
+
+The Unduplicator requires either PostHog Cloud, or a self-hosted PostHog instance running [version 1.30.0](https://posthog.com/blog/the-posthog-array-1-30-0) or later. 
+
+Not running 1.30.0? Find out [how to update your self-hosted PostHog deployment](https://posthog.com/docs/self-host/configure/upgrading-posthog)! 
+
+### How do I install the Unduplicator app for PostHog?
+
+1. Log in to your PostHog instance
+2. Click 'Apps' on the left-hand tool bar
+3. Search for 'Unduplicates' 
+4. Select the Unduplicator app, press 'Install'.
+5. Once the app is installed, press the blue button to configure the app and select which of the de-duplication methods you want to use (described above).
+
+### Is the source code for this app available?
+
+PostHog is open source and so are all apps on the platform. The [source code for the Unduplicator app](https://github.com/paolodamico/posthog-app-unduplicates) is available on GitHub. 
+
+### Who created this app?
+
+We'd like to thank former PostHog team member [Paolo D'Amico](https://github.com/paolodamico) for creating the Unduplicator. We miss you, Paolo!
+
+### What if I have feedback on this app?
+
+We love feature requests and feedback! Please [create an issue](https://github.com/PostHog/posthog/issues/new?assignees=&labels=enhancement%2C+feature&template=feature_request.md) to tell us what you think. 
+
+### What if my question isn't answered above?
+
+We love answering questions. Ask us anything via [our FAQ page](/questions).
+
+You can also [join the PostHog Community Slack group](/slack) to collaborate with others and get advice on developing your own PostHog apps.

contents/apps/unduplicator/index.mdx

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+---
+title: Unduplicator
+featuredImage: ../images/apps/unduplicator.png
+documentation: /apps/unduplicator/docs
+thumbnail: ../thumbnails/unduplicator.png
+filters: {
+    type: ["data-in"],
+    maintainer: community
+}
+---
+
+<Section
+    divider={false}
+    title="Clean up your data by removing duplicate events. Especially handy when importing historical data into PostHog."
+    size="full"
+    cols={2}
+>
+    <div>
+        <h5>Stay tidy, stay accurate</h5>
+        <p>Automatically remove any duplicate events, so your insights aren't swayed by bad data without your knowledge.</p>
+    </div>
+    <div>
+        <h5>Import old events cleanly</h5>
+        <p>Adding historical data to PostHog after ingestion has begun? The Unduplicator automatically cleans as you go.</p>
+    </div>
+</Section>
+
+<TutorialsSlider topic="unduplicator" />
+
+<Documentation />