Fixing AWS S3 Access Denied (403 Forbidden) – Step-by-Step Guide

If you’re working with Amazon S3 and get hit with the dreaded Access Denied (403) error, don’t panic. This is one of the most common S3 issues and usually boils down to permissions misconfiguration. This article will help you: Understand why this error happens, Troubleshoot common causes, Apply working solutions with code examples and AWS Console screenshots. Avoid it in future deployments

AWS

8/3/20252 min read

What Triggers S3 Access Denied (403)?

The error usually looks like this:

This happens when:

The IAM user/role lacks s3:* permissions

S3 Bucket Policies restrict access

Public access is blocked at the bucket/account level

You're accessing a bucket in the wrong AWS region

There's a mismatch in signed URL or object ACLs

1. Check IAM Permissions (The Usual Suspect)

Steps:

  1. Go to IAM > Users > [your user] > Permissions

  2. Ensure the attached policy includes actions like:

    • s3:GetObject

    • s3:PutObject

    • s3:ListBucket (for listing files)

2. Check the Bucket Policy (It Might Be Blocking You)

Go to S3 > [Your Bucket] > Permissions > Bucket Policy

Example of a Restrictive Policy

This denies everyone, including you.

Fix:

Remove or modify the Deny statement to allow specific users or roles access.

Sample Open Access Bucket Policy (with caution)

Example IAM Policy

3. Disable “Block All Public Access” (If Hosting Public Content)

Even if you set a public policy, AWS will override it if this setting is ON.

Steps:

  1. Go to S3 > Bucket > Permissions > Block public access

  2. Click Edit

  3. Uncheck the settings as needed

  4. Save

🛑 Use this only if your use case requires public file access (like a static website)

4. Signed URLs: Common Pitfall

If you're using pre-signed URLs, a mismatch in the bucket name, region, or expiry can also result in 403.

Things to check:

  • Is the URL expired?

  • Is the bucket name correctly included?

  • Are you using the correct AWS region?

🧪 Test signed URL manually by visiting it in incognito mode.

5. Object ACLs – File-level Access Denied

Even if IAM and Bucket policies are okay, object-level ACLs might block you.

Steps:

  • Go to S3 > Bucket > Objects

  • Click on the object, go to Permissions

  • Make sure it has read permissions for intended users/public

Add Public ACL (if required)

Real-World Example: Fixing S3 403 for a Static Website

Let's say you're hosting a static site on S3 and hit Access Denied when visiting https://my-bucket.s3.amazonaws.com/index.html.

Checklist:

  • Bucket is public

  • index.html exists

  • Bucket policy allows s3:GetObject

  • Block Public Access is disabled

  • The region matches the endpoint

Once these are fixed, the site loads correctly.

Summary: Troubleshooting S3 Access Denied (403)

Final Tip: Use AWS Policy Simulator

Test your IAM + Bucket policies with the AWS Policy Simulator. It saves a lot of guesswork.