Hello,
First, letâs take a deep breath. That is an incredibly frustrating place to be. Firestore rules are one of the most powerful, but also most precise, parts of the platform.
Your app, your logic, and all your hard work are not destroyed. Youâve just run into a mismatch between your appâs logic and the security logic. Youâre right at the finish line, and this is just the last hurdle.
Why This Can Be Challenging
It sounds like youâre running into a common challenge: security rules require perfect precision, and it can be difficult to describe complex app logic in a way that generates the exact rules you need.
The AI agent is a fantastic tool for generating rules, but for debugging why a specific query is failing, the Rules Playground in the Firebase console is your most powerful asset.
The core of the problem is always that your appâs query (e.g., db.collection("posts").get()) and your security rules (e.g., allow read: if request.auth.uid == resource.data.userId;) are not in perfect alignment. When they donât match, your app just gets a âpermission deniedâ error, and itâs not obvious why.
How to Debug This (The Pro Method)
Letâs find the exact line thatâs causing the problem.
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Go to your Firebase Console â Firestore Database â Rules tab.
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On the right, youâll see the Rules Playground (or âSimulatorâ).
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This tool lets you simulate any request from your app to see precisely which line of your rules allows or denies it.
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Think about the query thatâs failing in your app. For example, letâs say itâs trying to read a list of posts from a posts collection.
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Re-create that exact request in the simulator:
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Simulation type: Set this to get (for a single doc) or query (for a list, like getDocs(collection(...))).
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Location: Type the path, like /posts.
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Authentication: This is the most important part. Toggle it ON.
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Provider: google.com (or password, it doesnât matter).
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Authenticated UID: Put in a real uid from your Authentication tab (e.g., my-test-user-id).
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Click Run.
The simulator will give you one of two answers:
If itâs red, it will highlight the exact line in your rules that blocked the request. This is the key! Thatâs the line you need to fix or adjust.
How We Can Help You
Youâre not in this alone. To help you, we need to see the two things that are misaligned:
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Your Rules: Post the relevant part of your firestore.rules file (e.g., the match /myCollection/{docId} { ... } block thatâs failing).
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Your App Code: Post the exact query from your app (e.g., the db.collection("posts").where("userId", "==", auth.currentUser.uid).get()) that is being denied.
With those two pieces of information, we can spot the mismatch in minutes.
The âBuild-Upâ Strategy (A Fresh Start)
If your rules have become overly complex and youâre not sure where the logic went wrong, sometimes the best approach is to start from a clean, secure foundation and build up.
Start with this (which denies all access, the most secure default):
Code snippet
rules_version = '2';
service cloud.firestore {
match /databases/{database}/documents {
// Deny all reads and writes by default
match /{document=**} {
allow read, write: if false;
}
}
}
Now, add one rule at a time. For example, letâs allow anyone who is signed in to read posts:
Code snippet
rules_version = '2';
service cloud.firestore {
match /databases/{database}/documents {
// Deny all reads and writes by default
match /{document=**} {
allow read, write: if false;
}
// Add this one new rule
match /posts/{postId} {
allow read: if request.auth != null;
}
}
}
Deploy it. Test it (in your app and the simulator). Does it work? Great. Now add the next rule (e.g., allow create). This âbuild-upâ method is much safer and easier to debug than trying to fix a complex set of generated rules.
Hang in there. You are much closer than you think, and weâre here to help.
