> For the complete documentation index, see [llms.txt](https://docs.whalesync.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.whalesync.com/features/two-way-sync.md).

# Two-way sync

Sync data bi-directionally between apps

<figure><img src="https://2481481593-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FtLaMDbvbGOow76E8CnqW%2Fuploads%2Fgit-blob-05222c7e916b9cafeca89d0909d7d12872942648%2Ftwo-way%20sync.png?alt=media" alt=""><figcaption></figcaption></figure>

Whalesync offers true two-way sync. Once set up, you can update data in either connected app and it will sync to the other in real-time.

When creating a new Whalesync base, two-way sync is easy to configure. Simply toggle the direction arrows to two-way:

<figure><img src="https://2481481593-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FtLaMDbvbGOow76E8CnqW%2Fuploads%2Fgit-blob-1d045e64f7a196114c7ce36e5ac0dc27ad3717f3%2Ftwo-way.gif?alt=media" alt=""><figcaption></figcaption></figure>

### Read-Only Fields

{% hint style="info" %}
**Two-way sync is not compatible with "read-only" field types**
{% endhint %}

There are certain field types you cannot sync data into. For example, a formula field cannot be overwritten. We call these "read-only" field types and tag them in the setup flow:

<figure><img src="https://2481481593-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FtLaMDbvbGOow76E8CnqW%2Fuploads%2Fgit-blob-d64156e6921a9d7b2f0eb723c9181bebdf82865a%2FRead%20Only.png?alt=media" alt=""><figcaption></figcaption></figure>

If you map a read-only field and choose two-way sync, that read-only field will be one-way while the rest of your fields remain two-way.

The built-in "\<App> Record ID" field is a read-only field that is worth mapping. Each app's Record ID flows one-way into a text field on the other side, and the rest of the table stays two-way. See [Store record IDs on both sides](/features/store-record-ids-on-both-sides.md).

| Example read-only field types |
| ----------------------------- |
| Formula                       |
| Lookup                        |
| Rollout                       |
| Count                         |
| Created Time                  |
| Last Modified Time            |
| Autonumber                    |