Why do download bars show 100% for more than 0 seconds?
In: Technology
Usually the percentage is calculated based on the trending history, so if it pauses towards the end it could just be that the DL slowed down.
Also at the very end it can pause because your virus scanner is checking the now complete file before the program signals that it’s completed.
If you have a slow disk, it can also be flushing part of the file from memory to the hard drive.
Could be a few reasons depending on the program. Maybe rounding up from 99.5%. Maybe after it’s downloaded it takes a bit to shut down or switch from download to installation mode. Maybe it does the entire installation during the 100%.
Progress bars are never an exact science. There’s no way to accurately calculate exactly how long something will take. Say you want to copy 100 files from one folder to another. You could go okay 100 files and each folder is 1% but obviously not all files are the same size. You could calculate the totally data size to transfer but disk read and write rates fluctuate sightly and there’s also overhead to create a new file. There’s always things like flushing file write caches etc. Basically it’s just not an exact science
Usually, progress bars are just junk, that is needed to make the best user experience.
It’s really rare when a progress bar used as a progress bar
Edit: sorry, I don’t notice that you were asking about a download bar. If the download bar is getting 100% less than 0 seconds, it doesn’t download anything. Or you just have ultra-speed net
Progress bars, whether for downloads, uploads, or program loading, sometimes bear no relation at all to actual progress. Videogames were particularly guilty of this. It doesn’t show progress at all, it just mollifies the frustrated human waiting for the process to complete.
In addition to what others have mentioned about general inaccuracy in progress meters, once the file has been 100% received, your system kicks off a few processes to check if the file is safe. First, it will compute a signature (hash) of the file and send it to one or more public servers run by Google, Microsoft, etc. which check to see if the hash is a common one (a frequently downloaded file is more likely to be safe), or if it matches any known malware downloads. On desktop operating systems, your anti-virus software will also activate to analyze the file to look for any suspicious markers that could indicate malware. During these processes, the download is progress is locked at “100% downloaded (but still not finished)” so you can’t accidentally run any malware before it has passed all the tests.
In most cases, it’s because the *download* has finished… the file has transferred to your PC. But it’s usually either saved into memory, or more usually saved to a temporary location
It then takes a few seconds to verify the file (to make sure it hasn’t been corrupted) and to save it to disk/rename/move it to the right location.
It’s rare for this to be taken into account in the download/saving percentage, because the actual physical download is complete.
Once it’s downloaded the app needs to do something with it and nobody thought it was worth the bother to add a “_Doing something with what just downloaded_” alert.
The popup window can only close when the file has been downloaded AND processed. The processing of a downloaded file can involve many things, but most commonly it just means the file is being written to the storage medium.
The download bar itself only tracks the actual download, not the part where it processes the downloaded data. Some programs will actually use a [second progressbar](https://i.stack.imgur.com/fHRaT.jpg) when the processing is expected to take a long time, but for the most part it happens fast enough that you don’t need an extra visual indicator.
The processing itself is quite unpredictable though, because it depends on the speed of your storage medium, the amount of the downloaded data that still needs to be processed, as well as system interrupts such as an antivirus checking if the data that is being written is actually safe.
If you have an SSD, then it should take less time to save the file (aka. moving it from a temp folder to the destination folder) or renaming it from something like yourfile.exe.part to yourfile.exe, if you have an HDD it should take a bit longer depending on how defragmented your hard drive is. In other words, how easy it is to put on your hard drive new files given that there’s enough space for it.
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