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AWS IAM Policy Size Exceeded Fix

DodaTech Updated 2026-06-24 2 min read

In this tutorial, you'll learn about AWS IAM Policy Size Exceeded Fix. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

You attach an IAM policy and get PolicySizeExceeded — the policy document exceeds the 6,144-character limit for customer managed policies or 1,024-character limit for inline policies.

Step-by-Step Fix

1. Check the current policy size

aws iam get-policy --policy-arn arn:aws:iam::123456789012:policy/MyPolicy --query 'Policy.{Arn:Arn,Description:Description}'
aws iam get-policy-version --policy-arn arn:aws:iam::123456789012:policy/MyPolicy --version-id v1 --query 'PolicyVersion.Document'

Expected output shows the policy document that needs trimming.

2. Split into multiple managed policies

// Wrong: one massive policy with all permissions
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": ["s3:*", "ec2:*", "lambda:*", "dynamodb:*", "sqs:*", "sns:*"],
            "Resource": "*"
        }
    ]
}

// Right: split into service-specific policies
{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": ["s3:GetObject", "s3:PutObject", "s3:ListBucket"],
            "Resource": ["arn:aws:s3:::my-bucket", "arn:aws:s3:::my-bucket/*"]
        }
    ]
}

3. Use wildcards to consolidate actions

// Wrong: listing every action individually
{
    "Effect": "Allow",
    "Action": [
        "s3:GetObject",
        "s3:PutObject",
        "s3:DeleteObject",
        "s3:ListBucket",
        "s3:GetBucketLocation]
    ],
    "Resource": "arn:aws:s3:::my-bucket/*"
}

// Right: use s3:Object* wildcard for object operations
{
    "Effect": "Allow",
    "Action": ["s3:GetObject", "s3:PutObject", "s3:ListBucket"],
    "Resource": "arn:aws:s3:::my-bucket/*"
}

4. Use AWS managed policies instead

aws iam list-attached-user-policies --user-name myuser

Expected output:

{
    "AttachedPolicies": [
        {"PolicyName": "AmazonS3FullAccess", "PolicyArn": "arn:aws:iam::aws:policy/AmazonS3FullAccess"}
    ]
}

5. Attach multiple policies to a group

aws iam create-group --group-name S3Admins
aws iam attach-group-policy --group-name S3Admins --policy-arn arn:aws:iam::aws:policy/AmazonS3FullAccess
aws iam attach-group-policy --group-name S3Admins --policy-arn arn:aws:iam::aws:policy/AmazonDynamoDBFullAccess
aws iam add-user-to-group --group-name S3Admins --user-name myuser

Prevention

  • Keep each policy under 4,000 characters to leave room for future additions.
  • Use AWS managed policies for standard permissions (S3 full access, Lambda basic execution).
  • Split permissions by service into separate policies.
  • Use IAM groups to attach multiple policies to users instead of inline policies.
  • Monitor policy size with the IAM Access Analyzer.

Common Mistakes with iam policy size

  1. Using foldl instead of foldl' causing stack overflow on large lists
  2. Forgetting deriving (Show, Eq) on custom data types needed for debugging
  3. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable

These mistakes appear frequently in real-world AWS code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

What is the IAM policy size limit?

Customer managed policies have a 6,144-character limit. Inline user/group policies have 1,024 characters. Inline role policies have 2,048 characters. |||Can I attach multiple policies to the same IAM user? Yes, an IAM user can have up to 10 managed policies and 2 inline policies attached. Use groups to manage larger permission sets. |||Does using shorter action names help reduce size? Yes, use wildcards like s3:Get* instead of listing every action. Also use compact JSON by removing whitespace and newlines.

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