Qt version 5.2.1

I think Noah used this version in his shipyard, and it was outdated when he set sails....
How about 6.8 for instance?

Qt version 5.2.1.

Are you aware just how old that version is (a decade)? Nobody here will be able to try on that, I suspect? That may be your final answer as to why it does not work, and you may have to use double if that works with that version.

At least as of 7 years ago see https://stackoverflow.com/questions/55044655/why-is-qtsettings-storing-floats-in-a-weird-mode-what-am-missing . For your version that is the "answer" --- or someone's best guess at the reason. Sounds like it may have changed in more recent versions.

Please do this before dealing with reading text and converting back, if that is what you do. One thing at a time! Let's see only what the problem writing a float to a .ini is, standalone. Then, depending, show the shortest possible complete, standalone code demonstrating your issue.

If you don't care about this and doubles do work, don't forget like Christian said you can save as a double and deal with assigning it to float on reading.

float flt = 1.0f;
settings.setValue("flt", flt);
// stored in a .ini file as
flt=1

then I don't know where/why the OP comes up with @QVariant(\0\0\0\x87=\xcc\xcc\xcd in the output/.ini/text file in the first place? Unless by any chance it depends on the value in flt rather than a simple 1.

@Christian-Ehrlicher
I agree, but his problem will be that it will deserialize as a QVariant(double) where he presumably requires it to be QVariant(float)? So he may need to do some massaging.

I don't understand - QSettings returns a QVariant. QVariant has toFloat()...

And this works fine for me with Qt6.11

double dbl = 1.0;
float flt = 1.0f;
QSettings settings("D:/tmp.ini", QSettings::IniFormat);
settings.setValue("dbl", dbl);
settings.setValue("flt", flt);

-->

[General]
dbl=1
flt=1

Results in the text file look like this: "@QVariant(\0\0\0\x87=\xcc\xcc\xcd", which is not acceptable.

So that I understand. What is "not acceptable"? Assuming that value is correct, and deserializes correctly, that is all Settings is supposed to do. Are you saying something like you want to impose requirements on its output (to a file or registry) such that it is human-readable to you?