Adalo external collection not working: common causes and fixes
If an Adalo external collection is not working, check four things in order: the endpoint returns a flat JSON array (not a wrapped or nested object), every record includes every property, the API honours the offset and limit parameters Adalo sends, and the total count it reports stays the same across pages. Those four cover the large majority of failures.
External collections fail in a small number of predictable ways. Work through these in order, each check rules out a whole category of problem, so you narrow it down fast.
Step 1: Open the endpoint outside Adalo
Paste the URL into a browser or API client with the same headers Adalo uses. This separates "my API is wrong" from "my Adalo setup is wrong".
- No response or an error → fix the API before touching Adalo.
- Not valid JSON → fix the API response format.
- Valid, flat JSON → the problem is likely on the Adalo side.
Step 2: No properties detected
Adalo builds the property list from the first page of records only.
- Records nested inside another object never become properties.
- Nulls in place of real values on the first page can hide a property.
- Return flat records with real values in the first page of results.
Step 3: The count is wrong or lists stop loading
Adalo relies on the total your API reports plus consistent pagination.
- A total that changes between pages makes Adalo stop loading early.
- Ignoring the offset parameter makes Adalo repeat page one forever.
- Return the same, accurate total on every single page.
Step 4: The list is empty in preview but the test passed
A passing connection test does not guarantee the list on screen shows anything.
- Check the list is bound to the external collection, not a leftover internal one.
- Look for a filter comparing a Text property to a Number.
- Check a Logged-in User filter is not being hit while logged out.
- Strip filters, confirm records appear, then add filters back one by one.
Step 5: Changes do not appear
Adalo caches the property list, so API-side changes need a manual refresh.
- Re-run the connection test on your endpoint first.
- Refresh the collection in Adalo so it re-reads the properties.
- A property that vanished from screens was likely renamed, not added.
Common mistakes and how to diagnose them
"No properties found" when adding the collection.
- Likely cause:
- Response is { "data": [...] } or records contain nested objects.
- Fix:
- Return a top-level array of flat objects, or point Adalo at the array path if your setup supports it.
Collection connects, list shows nothing.
- Likely cause:
- A filter mismatch, or the list bound to the wrong collection.
- Fix:
- Strip every filter, confirm records appear, then reapply filters one at a time.
Item count is wrong or scrolling repeats records.
- Likely cause:
- Pagination ignored, or the total recalculated per request.
- Fix:
- Apply offset/limit exactly as sent and return a stable total on every page.
Works in the editor, fails in the published app.
- Likely cause:
- Missing CORS headers, or an API key restricted to your own IP or origin.
- Fix:
- Allow requests from the published domain and test on a real device before assuming it is fixed.
A Number property will not sort correctly.
- Likely cause:
- The value is a string in the JSON ("19.99" instead of 19.99).
- Fix:
- Return real JSON numbers and refresh the collection so Adalo re-reads the type.
Real example: 3,000 records, Adalo showed 20
An orders dashboard connected fine, showed the right properties, then refused to load past the first page. The API returned "total": records.length, the length of the current page, not the collection.
Because that number was 20 on every request, Adalo believed it had everything after one call. Returning the true total fixed the list without touching a single screen. Wrong counts almost always trace back to the total, not the pagination itself.
When you need an Adalo expert
Plenty of Adalo issues are straightforward to fix yourself with the steps above. It usually pays to bring in an experienced Adalo developer when the problem sits deeper in the build:
- The endpoint returns valid JSON but Adalo still refuses to read it, and you have already ruled out shape and pagination.
- The collection behaves differently in preview, the web app and the native build.
- You cannot change the API you are consuming and need a translation layer in front of it.
- The app is live and the broken collection is affecting real users.
Related guides
How to connect an external collection to Adalo
Step-by-step: get a REST endpoint Adalo accepts, add it under Database → External Collection, and bind the properties to your lists and forms.
How to connect an API to Adalo
Connect a REST API to Adalo with custom actions or external collections, including the response shape, authentication headers and pagination Adalo expects.
How to debug an Adalo app
A repeatable way to find why an Adalo list is empty, an action does nothing, or a form saves the wrong record, checked in the same order every time.
How to set up a custom action in Adalo
Create an Adalo custom action step by step: method, URL, headers, body with magic text, and how to use the response on the next screen.
Frequently asked questions
Why does my Adalo external collection show no properties?
The response is not a flat JSON array, or the first records omit properties. Adalo reads property names from the first page only.
Can I use filters on an external collection?
Yes, on top-level properties. Filters through relationships are unreliable on external collections.
Why does my list stop after the first page?
Your API is reporting a total that matches the page size instead of the full record count.
Do I need to re-add the collection after changing properties?
No, refresh it. Re-adding creates a second collection and orphans the bindings on your screens.
Why does it work in preview but not in the published app?
Usually CORS or an origin-restricted API key. Allow the published domain and retest on a device.
Can Adalo read XML instead of JSON?
No. Convert the response to JSON before Adalo sees it.
Webnux Tools is an independent product by Webnux Ltd. It is not affiliated with, endorsed by, or sponsored by Adalo, Inc. Adalo is a trademark of Adalo, Inc.