File extension and real format: what is the difference
File with the name photo.jpg It can contain PNG or HEIC. Let's figure out why changing the extension does not replace the conversion and how the site determines the uploaded images.
What does the extension mean
Extension — the part of the name after the last dot. It helps applications choose how to open a file. The MIME type is a separate designation of the content type, for example, image/JPEG. The name and the transmitted type may not match the data.
What does renaming do
If replaced .HEIC on .JPG, the same data will remain inside. The app may show an error instead of a photo. The conversion reads the original image and creates a new file with a different encoding.
How our converter checks
When adding a file, the site reads its initial bytes and looks for signs of supported formats. A certain type appears in the queue, even if the extension is erroneous. This is pre-recognition: full verification occurs during decoding.
Why does the recognized file sometimes not open
The header may be saved in a corrupted file. In addition, one format has different options: for example, support for regular TIFF does not mean support for BigTIFF. In this case, the text of the error is important, not the renaming.
When a different extension means the same format
JPG and JPEG, TIF and TIFF are variants of extensions of the same formats. To change the compression method or pixels, you still need to process the content. Keep a copy of the original before any name changes.