Logs

The build scripts print only the build progress to the console. The full build output is redirected to the build.log file, so if you encounter an error, that is the first file to look at. It shows you why the build failed.

Sometimes the details in build.log are not enough to understand the root cause of a failure. In those cases, check the configuration log (config.log) of the library that was being compiled at that moment. For every library except ffmpeg, this file is located at src/<library>/config.log; for ffmpeg, it is at src/ffmpeg/ffbuild/config.log.

You can also follow the build progress from build.log by filtering for INFO events, like below.

INFO: Using BISON at /nix/store/0nr454gcds29s3jx66p3vy88vg2qcdvy-bison-3.8.2/bin/bison
INFO: Using MESON at /nix/store/vz08ca9zyjnh7krqzg63yn93rmiv9hnb-meson-1.7.2/bin/meson
INFO: Using SED at /nix/store/gwn9326rlnzwj7k4g44s3sxf9x7v9bpp-gnused-4.9/bin/sed
INFO: Using PKG_CONFIG_LIBDIR at /nix/store/lhv5bqfm5ywzrwqf0zyzk5gr88z5yy71-zlib-1.3.1-dev/lib/pkgconfig:/nix/store/lhv5bqfm5ywzrwqf0zyzk5gr88z5yy71-zlib-1.3.1-dev/share/pkgconfig
INFO: Active path: /Applications/Xcode.app/Contents/Developer
INFO: CC: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
INFO: Using SDK 26.2 by Xcode provided at /Applications/Xcode.app/Contents/Developer
INFO: Build options: --enable-harfbuzz --enable-libass --disable-arm64e -x --spm
INFO: Disabled armv7 architecture which is not supported with Min iOS Target 12.1 and Min Mac Catalyst Target 14.0 on iOS SDK 26.2
INFO: Disabled armv7s architecture which is not supported with Min iOS Target 12.1 and Min Mac Catalyst Target 14.0 on iOS SDK 26.2
INFO: Disabled i386 architecture which is not supported with Min iOS Target 12.1 and Min Mac Catalyst Target 14.0 on iOS SDK 26.2
INFO: Building ffmpeg-kit-next v8.1.0-2-gd6d127d for iOS: Sun  5 Jul 2026 01:55:51 +03
INFO: Custom library 1 not detected
INFO: libjxl library downloaded
INFO: Starting new build for arm64 targeting iOS SDK 12.1 and Mac Catalyst 14.0 at Sun  5 Jul 2026 01:56:26 +03
INFO: Enabled library fontconfig will be built
INFO: Enabled library expat will be built
INFO: Enabled library harfbuzz will be built
INFO: Enabled library libjxl will be built