Hello to all.

In Debug mode, when outputting text to the Serial, leading spaces are removed.
In Release mode, they are not removed. 
Serial output is not important for me, but the same happens when html page is sent to the browser by command:
server.send(200, "text/html", output_buffer);

The result is extra traffic, and in a large program this causes even more Memory Usage in release mode than in debug mode (maybe by another reason)
Release:
Program size: 370 328 bytes (used 35% of a 1 044 464 byte maximum) (55.32 secs)
Minimum Memory Usage: 61780 bytes (75% of a 81920 byte maximum)

Debug:
Program size: 372 652 bytes (used 36% of a 1 044 464 byte maximum) (34.19 secs)
Minimum Memory Usage: 59800 bytes (73% of a 81920 byte maximum)

Is there some option (or another way) to enable removing extra spaces in Release mode too and decrease Memory Usage?
I use VMicro with Visual Studio 2013 for programming ESP8266 chip (D1 mini).

I suspect that some #define in your code is removing the spaces because I can not relate the http send to anything Visual Micro does other than some define being set.

What board options selection have you made between the two types of build?

If you re unsure then follow the guide in the yellow box above and submit two .txt files one for Release and one for Debug.