Building for iOS Simulator, but the linked framework '****.framework' was built for iOS

Question

Xcode 12.3

In my case I solved this problem by simply setting Validate Workspace to Yes in the Build Settings tab

No doubt that the fix in case of Xcode 12.3 is to setup the Validate Workspace property in the target's build setting. However if you check the diff after this change, the reason of the build error is the missing parameter (VALIDATE_WORKSPACE) from the project file, not the value of the parameter. So you don't need the value to be YES. You need to add the value to the project settings and you can leave it on the default value (NO). At the first time, it shows up in the Build Settings with NO, but only because that is the default value of the missing parameter.

TLDR; Without changing your project setup, go to your target's build settings, find "Validate Workspace", set it to YES, then set back to NO.

It happened to me when I added my custom framework into the project and after I updated my Xcode, I encountered the same issue.

Solution : under build settings in project search for Validate workspace Just change to yes which is by default set to no

Use a .xcframework rather than a "fat" .framework containing an iOS and iOS simulator slice. This also obviates the need to use a build phase to strip the iOS simulator slice when building for the App Store.

"Fat" frameworks, which are typically created using lipo as they cannot be built directly by Xcode, are not supported (source: Developer Technical Support Apple Developer forum). .xcframework is the only supported mechanism to ship a single framework supporting both iOS and the iOS simulator.

Also .xframework's is the only supported way to ship a binary Swift framework (source: Developer Technical Support on Apple Developer forum).

In Xcode 12.3, the fact that "fat" frameworks are non supported is enforced, as Xcode verifies the frameworks during build, which is why a lot of projects suddenly started to see build errors.

Most answers here are for consumers of universal binaries to work around the new restrictions. But, as in noted elsewhere, it's time to migrate to Apple's XCFramework format for framework authors.

If you were running a custom build script to create universal binary before with an aggregate target and lipo, it's straightforward to migrate to producing .xcframework files

First, in build settings make sure "Build Libraries for Distribution" (BUILD_LIBRARY_FOR_DISTRIBUTION) is set to YES

Then, replace your existing aggregate target build script that used lipo with something like the following which is simple for showing how to make "release" frameworks only:

# Universal Script

set -e

FRAMEWORK_NAME="your_framework_name"
IOS_SCHEME_NAME="your_scheme_name"

if [ -d "${SRCROOT}/build" ]; then
rm -rf "${SRCROOT}/build"
fi

SIMULATOR_ARCHIVE_PATH="${SRCROOT}/build/${FRAMEWORK_NAME}-iphonesimulator.xcarchive"
DEVICE_ARCHIVE_PATH="${SRCROOT}/build/${FRAMEWORK_NAME}-iphoneos.xcarchive"

OUTPUT_DIR="${SRCROOT}/framework_out_universal/"

# Simulator xcarchieve
xcodebuild archive \
  -scheme ${IOS_SCHEME_NAME} \
  -archivePath ${SIMULATOR_ARCHIVE_PATH} \
  -configuration Release \
  -sdk iphonesimulator \
  SKIP_INSTALL=NO

# Device xcarchieve
xcodebuild archive \
  -scheme ${IOS_SCHEME_NAME} \
  -archivePath ${DEVICE_ARCHIVE_PATH} \
  -sdk iphoneos \
  -configuration Release \
  SKIP_INSTALL=NO

# Clean up old output directory
rm -rf "${OUTPUT_DIR}"

# Create xcframwork combine of all frameworks
xcodebuild -create-xcframework \
  -framework ${SIMULATOR_ARCHIVE_PATH}/Products/Library/Frameworks/${FRAMEWORK_NAME}.framework \
  -framework ${DEVICE_ARCHIVE_PATH}/Products/Library/Frameworks/${FRAMEWORK_NAME}.framework \
  -output ${OUTPUT_DIR}/${FRAMEWORK_NAME}.xcframework

# Delete the most recent build.
if [ -d "${SRCROOT}/build" ]; then
rm -rf "${SRCROOT}/build"
fi

You can tweak the above to have different output dirs, different deletion behavior, support multiple configurations (Release vs Debug) but this works for me.

Finally, as a one time step, delete the your_framework_name.framework universal binary that caused you the error as mention in this project. Copy the newly built your_framework_name.xcframework and add it to the project and the error should go away.

possible reason would be

1. framework which you are using may not be built for simulator architecture(x86_64), you can check the compatibility by going to framework folder (framework_name.framework --> modules --->framework_name.swiiftModule-->) in this path you should see arm/i386/x86_64 support files
2. if you have updated to new Xcode, the frameworks you are using are not compatible to the newer compiler version, so vendor needs to share the recent compatible one, in this case you will not be able to run on both device and simulator

If you are using Carthage, make sure you use the copy-frameworks script rather than using Embed & Sign as embedded content. I was getting this same error because I forgot about that.