The size of item attachments is not consistently displayed on the item details page in ArcGIS Online.

Workaround

Currently, there exists only a partial workaround for the issue. The attachment size can be accurately acquired under all circumstances via the Python API. Run a script similar to the one seen in the screenshot below to calculate consistently accurate attachment sizes. Currently, the Python API cannot calculate file sizes under many circumstances; it is only known to work when both the file size and the attachment size are present on the item details page.

If the file size is 0 KB on the item details page, the Python API is unable to calculate it correctly. The result often comes in the form of a negative value or a nonsensical value, as shown in the screenshot below. The file size is always significantly smaller than the attachment size.

If attempting to calculate feature storage costs using this method, it is important to note that credits are calculated based on what is shown on the item details page. The value reflected on the items details page and related item reports is the value calculated for the credit consumption. Feature storage credit consumption is calculated hourly.

Even if the Python API shows the correct attachment size, the attachment size displayed on the item details page is used in storage calculation, even if it is at 0 KB. This means that customers may be undercharged for feature storage. Additionally, an accurate calculation of credit usage on a weekly or monthly basis is difficult if the Organization Status Dashboard is not working, as the fluctuation of sizes presented on the item details page causes credit usage to be inconsistent on an unpredictable basis. The item details page does not present sizes greater than the true file or attachment size, so customers do not need to worry about being overcharged for feature storage.

Steps to Reproduce