> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hightouch.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Resync, reset CDC, or clear and fill
> Full resync, reset CDC, and clear and fill are one-off run controls that change how the next run treats your data — they are not sync modes.
Each of these actions is high-risk in a different way, so choose based on what you need to happen on the next run. All three run from the sync's **...** menu — click **Resync or reset...** and pick an option.
## Choose an action
| Action | What it does | When to use it | Primary risk |
| - | - | - | - |
| [Full resync](#full-resync) | Reprocesses every row currently in the model as if it were newly **Added**, ignoring prior state. | Rebuild destination state when reprocessing every row is safe. | Duplicate records or repeated events for insert-mode syncs, event syncs, and webhook destinations. |
| [Reset CDC](#reset-cdc) | Clears change-data-capture state without sending the reset run's rows. | Re-establish a fresh baseline when you don't want a backfill. | The destination can drift, because the skipped changes are never sent. |
| [Clear and fill](#clear-and-fill) | Clears the destination list or segment, then re-fills it from the current model. | Rebuild a replaceable audience or segment. | A temporary empty state, and it clears the entire list — not only the records Hightouch added. |
## Full resync
A full resync — labeled **Resync full query** in the menu — resets the sync's tracking to its initial state, as if it were syncing for the first time. It processes every row currently in the model as an **Added** row.
By default, Hightouch tracks changes between runs and [sends only the necessary updates](https://docs.hightouch.com/getting-started/concepts.md#change-data-capture-cdc), so an initial run shows many **Added** rows and later runs show mostly **Changed** or **Removed**. A full resync returns the sync to that initial all-**Added** state.
### Before you begin
You need a sync that has run at least once. Check the following before you trigger a full resync:
| Criteria | Explanation |
| - | - |
| [Sync mode](https://docs.hightouch.com/syncs/types-and-modes.md#sync-modes) | - [**Update** or **upsert**](https://docs.hightouch.com/syncs/types-and-modes.md#sync-modes) syncs are safe to fully resync: an already-synced row updates the same record.
- [**Insert**](https://docs.hightouch.com/syncs/types-and-modes.md#sync-modes) syncs, [event syncs](https://docs.hightouch.com/syncs/types-and-modes.md#event-syncs), and [webhook destinations](https://docs.hightouch.com/destinations/http-request.md) aren't recommended, because reprocessing rows can create duplicates.
|
| [Delete behavior](https://docs.hightouch.com/syncs/overview.md#delete-behavior) | - If your destination supports deleting records and you selected **Do nothing** when records leave the query results, a full resync has no impact on deletes.
- If you selected **Clear fields** or **Delete destination record**, that setting is ignored during a full resync. A full resync only processes rows that currently exist in the model, so there's no [diffing](https://docs.hightouch.com/syncs/cdc.md) against the prior run to identify what was removed. **Removed** rows are ignored even when delete behavior is enabled.
|
> [!WARNING]
>
> A full resync can create duplicates or other issues in your destination if the
> prerequisites above aren't met.
## Reset CDC
Reset CDC clears [change data capture](https://docs.hightouch.com/syncs/cdc.md) state without resyncing records. Hightouch ignores the current state of your model and tracks only rows added, changed, or removed from now on. The next run captures a fresh snapshot of your model and sends nothing to the destination; runs after that send only new changes.
Reset CDC suits insert-only use cases like conversion events and operational alerts, where a backfill would create duplicate records.
> [!WARNING]
>
> Skipping the backfill can leave your destination out of sync with your model,
> because the changes in the reset run are never sent. Use Reset CDC only when
> that drift is acceptable.
## Clear and fill
When the destination supports clearing all records in a segment or audience, the **Resync or reset...** modal offers a clear-and-fill option, **Clear list and trigger full resync**. It works like a [full resync](#full-resync) with one added step: before it reprocesses the model's rows, it clears every user or identifier from the segment or audience selected in the sync configuration.
> [!WARNING]
>
> This clears the entire list, not only the records Hightouch added. It can undo
> changes made by other tools managing that list, and the clear step can take
> several hours to complete.
## Verify the result
After the run finishes, open it from the [**Runs** tab](https://docs.hightouch.com/syncs/debugger.md#view-run-details) and confirm it did what you expected:
* **Full resync** — every row shows as **Added**, and the operation count matches your model's row count.
* **Reset CDC** — the run sent nothing to the destination (zero operations); the next scheduled run resumes normal diffing.
* **Clear and fill** — the list emptied and then refilled to the current model's row count.
If the result isn't what you expected, use the [debugger](https://docs.hightouch.com/syncs/debugger.md) to inspect the run.