When inventory gets synced
When syncing happens
SKU Stock Sync updates inventory after it detects a relevant inventory change. That usually means a product, variant, or inventory item in Shopify changed stock, and that change gave the app a reason to sync.
Syncing is event-driven. In plain language, that means the app does not keep doing full-store sweeps looking at every item in your store. Instead, it waits for inventory-related events, then processes the SKU groups that were affected.
When a stock change happens for an item that belongs to a SKU group with other members, that group may be marked as due for syncing. Due simply means the group has been flagged as needing attention the next time the app processes pending sync work.
Due groups are processed on two schedules:
Regular schedule: the normal ongoing processing for groups that became due.
Daily schedule: an additional scheduled pass that also processes due groups.
This means inventory changes are picked up and synced on a schedule, not always the moment the change happens.
If helpful, think of syncing as a queue. Inventory changes can put a group into the queue, and the app processes that queue on its schedules or when you run a manual sync.
If you want to understand the bigger picture of how groups and syncing work together, see How syncing works.
Why syncing may not happen immediately
The most important expectation to set is this: SKU Stock Sync is not instant. A detected change does not always produce an immediate stock update.
That delay is expected because the app processes due groups on scheduled runs instead of continuously rechecking your whole catalog.
You can also process due groups sooner from the Sync page by running a manual sync. Manual sync handles groups that are already due and processes them right away, instead of waiting for the next scheduled run. See Manual syncing.
If you know inventory changed recently and want the app to act on it sooner, use manual sync from the Sync page. This is the fastest way to process groups that are already due.
Some groups may also be processed less often depending on how the app prioritizes work, especially for higher-stock groups. Even then, the main rule stays the same: the app syncs based on detected changes and scheduled processing, not constant full-store rescans.
Why there may be nothing to sync
If no relevant inventory change has happened, there may be nothing for SKU Stock Sync to do.
This is often the reason a sync appears quiet: the app only processes groups that became due. If nothing made a group due, there may be no changes waiting.
If stock changed but a group did not become due, the most likely reasons are:
The item is still unknown to the app. Newly added products, variants, or SKU changes may need to be detected and prepared before the app can place them into the right group and sync them.
See Insights, to check if this has occured.
The group has only one member. Single-member groups are ignored, so they cannot become due for syncing.
If you recently added products, created variants, or changed SKUs, give the app time to detect and prepare those items first. You can learn more about keeping groups up to date in Creating and updating groups.
Being "prepared" means the app has recognized the item and sorted it into the correct SKU group structure so it can participate in syncing.
Changes that can trigger syncing
A sync can be triggered by more than just something you changed inside SKU Stock Sync.
Inventory changes from other apps, integrations, or direct actions in the Shopify admin can also cause a group to become due. For example, if stock is edited elsewhere and that change affects an item in a multi-member group, SKU Stock Sync may detect that event and schedule the group for syncing.
This is why you may sometimes see syncing happen after actions taken outside the app itself.
What can affect the final result
Sometimes SKU Stock Sync runs, but the final stock level you see in Shopify still looks unexpected. When that happens, timing is often only part of the story.
Other inventory apps can also change stock after SKU Stock Sync runs. If another app reacts to the updated quantity and changes it again, the final stock can look different from what you expected.
In some setups, this can even create back-and-forth changes where one app updates stock, another app reacts, and the quantity keeps getting adjusted repeatedly.
If another inventory app is also editing the same products or variants, it can override or counteract SKU Stock Sync. This can make stock levels look inconsistent even when syncing itself is working correctly.
If you suspect another app is involved, see Another app is changing inventory.
If inventory did not sync as expected
If syncing seems delayed or missing, the usual checks are:
Did a relevant inventory change actually happen?
Is the item already known to the app and prepared for grouping?
Is the item in a group with more than one member?
Did the group become due?
Has the regular schedule, daily schedule, or a manual sync had a chance to process it?
Is another app changing the stock afterward?
For a focused troubleshooting guide, see Inventory did not sync.