Protect custom backend resources with App Check on Apple platforms
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You can useApp Checkto protect non-Google custom backend resources for
your app, like your own self-hosted backend. To do so, you'll need to do both of
the following:
Modify your app client to send anApp Checktoken along with each request
to your backend, as described on this page.
To ensure your backend requests include a valid, unexpired,App Checktoken,
wrap each request in a call toAppCheck.token(). TheApp Checklibrary
will refresh the token if necessary, and you can access the token in the
method's completion block.
Once you have a valid token, send it along with the request to your backend. The
specifics of how you accomplish this are up to you, butdon't sendApp Checktokens as part of URLs, including in query parameters, as this
makes them vulnerable to accidental leakage and interception. The following
example sends the token in a custom HTTP header, which is the recommended
approach.
Swift
do{lettoken=tryawaitAppCheck.appCheck().token(forcingRefresh:false)// Get the raw App Check token string.lettokenString=token.token// Include the App Check token with requests to your server.leturl=URL(string:"https://yourbackend.example.com/yourApiEndpoint")!varrequest=URLRequest(url:url)request.httpMethod="GET"request.setValue(tokenString,forHTTPHeaderField:"X-Firebase-AppCheck")lettask=URLSession.shared.dataTask(with:request){data,response,errorin// Handle response from your backend.}task.resume()}catch(leterror){print("Unable to retrieve App Check token:\(error)")return}
Objective-C
[[FIRAppCheckappCheck]tokenForcingRefresh:NOcompletion:^(FIRAppCheckToken*_Nullabletoken,NSError*_Nullableerror){if(error!=nil){// Handle any errors if the token was not retrieved.NSLog(@"Unable to retrieve App Check token: %@",error);return;}if(token==nil){NSLog(@"Unable to retrieve App Check token.");return;}// Get the raw App Check token string.NSString*tokenString=token.token;// Include the App Check token with requests to your server.NSURL*url=[[NSURLalloc]initWithString:@"https://yourbackend.example.com/yourApiEndpoint"];NSMutableURLRequest*request=[[NSMutableURLRequestalloc]initWithURL:url];[requestsetHTTPMethod:@"GET"];[requestsetValue:tokenStringforHTTPHeaderField:@"X-Firebase-AppCheck"];NSURLSessionDataTask*task=[[NSURLSessionsharedSession]dataTaskWithRequest:requestcompletionHandler:^(NSData*_Nullabledata,NSURLResponse*_Nullableresponse,NSError*_Nullableerror){// Handle response from your backend.}];[taskresume];}];
Replay protection (beta)
When making a request to an endpoint for which you've enabledreplay protection,
wrap the request in a call tolimitedUseToken()instead oftoken():
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[],[],null,["You can use App Check to protect non-Google custom backend resources for\nyour app, like your own self-hosted backend. To do so, you'll need to do both of\nthe following:\n\n- Modify your app client to send an App Check token along with each request to your backend, as described on this page.\n- Modify your backend to require a valid App Check token with every request, as described in [Verify App Check tokens from a custom backend](/docs/app-check/custom-resource-backend).\n\nBefore you begin\n\nAdd App Check to your app, using either [App Attest](/docs/app-check/ios/app-attest-provider),\n[DeviceCheck](/docs/app-check/ios/devicecheck-provider), or a [custom provider](/docs/app-check/ios/custom-provider).\n\nSend App Check tokens with backend requests\n\nTo ensure your backend requests include a valid, unexpired, App Check token,\nwrap each request in a call to `AppCheck.token()`. The App Check library\nwill refresh the token if necessary, and you can access the token in the\nmethod's completion block.\n\nOnce you have a valid token, send it along with the request to your backend. The\nspecifics of how you accomplish this are up to you, but *don't send\nApp Check tokens as part of URLs*, including in query parameters, as this\nmakes them vulnerable to accidental leakage and interception. The following\nexample sends the token in a custom HTTP header, which is the recommended\napproach. \n\nSwift \n\n```swift\ndo {\n let token = try await AppCheck.appCheck().token(forcingRefresh: false)\n\n // Get the raw App Check token string.\n let tokenString = token.token\n\n // Include the App Check token with requests to your server.\n let url = URL(string: \"https://yourbackend.example.com/yourApiEndpoint\")!\n var request = URLRequest(url: url)\n request.httpMethod = \"GET\"\n request.setValue(tokenString, forHTTPHeaderField: \"X-Firebase-AppCheck\")\n\n let task = URLSession.shared.dataTask(with: request) { data, response, error in\n // Handle response from your backend.\n }\n task.resume()\n} catch(let error) {\n print(\"Unable to retrieve App Check token: \\(error)\")\n return\n}\n```\n\nObjective-C \n\n```objective-c\n[[FIRAppCheck appCheck] tokenForcingRefresh:NO\n completion:^(FIRAppCheckToken * _Nullable token,\n NSError * _Nullable error) {\n if (error != nil) {\n // Handle any errors if the token was not retrieved.\n NSLog(@\"Unable to retrieve App Check token: %@\", error);\n return;\n }\n if (token == nil) {\n NSLog(@\"Unable to retrieve App Check token.\");\n return;\n }\n\n // Get the raw App Check token string.\n NSString *tokenString = token.token;\n\n // Include the App Check token with requests to your server.\n NSURL *url = [[NSURL alloc] initWithString:@\"https://yourbackend.example.com/yourApiEndpoint\"];\n NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];\n [request setHTTPMethod:@\"GET\"];\n [request setValue:tokenString forHTTPHeaderField:@\"X-Firebase-AppCheck\"];\n\n NSURLSessionDataTask *task =\n [[NSURLSession sharedSession] dataTaskWithRequest:request\n completionHandler:^(NSData * _Nullable data,\n NSURLResponse * _Nullable response,\n NSError * _Nullable error) {\n // Handle response from your backend.\n }];\n [task resume];\n}];\n```\n\nReplay protection (beta)\n\nWhen making a request to an endpoint for which you've enabled\n[replay protection](/docs/app-check/custom-resource-backend#replay-protection),\nwrap the request in a call to `limitedUseToken()` instead of `token()`: \n\nSwift \n\n AppCheck.appCheck().limitedUseToken() { token, error in\n // ...\n }\n\nObjective-C \n\n [[FIRAppCheck appCheck] limitedUseTokenWithCompletion:^(FIRAppCheckToken * _Nullable token,\n NSError * _Nullable error) {\n // ...\n }];"]]
