Does ICO Entry Order Change the Extracted Image?
Reversing the directory order did not change the pixels in any matching ICO size in this controlled pair; Pillow 13.0.0 opened both at 256 by 256 pixels by default.
Measured November 2, 2026 with Python 3.12.14 and Pillow 13.0.0. This is a local file-and-reader experiment, not an online converter comparison or a browser compatibility test.
Does changing ICO entry order change the pixels inside each size?
Not in this controlled pair. The 32, 64 and 256 pixel PNG payloads have the same individual SHA-256 values in both containers, and each matching decoded RGBA array is identical. Only their directory and payload ordering was changed. This result does not establish what an online converter will select.
Are two 972-byte ICO files necessarily the same file?
No. These two files are each 972 bytes but differ at 732 byte positions. The ascending-order file has SHA-256 1f4828ba087f0beafd27b44eadd6234e0524c9647d8e8c718d867641b457412a; the descending-order file has SHA-256 53aed5dfd3eb556a140c46bd2eaf33bf9277389f686fe5126ed1865b17caa1cf. The per-size image payloads match; the containers do not.
Which image did the local reader open by default?
Pillow 13.0.0 with Python 3.12.14 opened both controlled files at 256 by 256 pixels. The center pixel was RGBA (20, 180, 90, 128) in each case. This is limited to the two fixtures, that reader and the November 2, 2026 test. Browser display and online-tool layer selection have not been tested.
