Introduction

To list all objects in an S3 bucket, you need to handle pagination. Large buckets are not returned in one response, so the correct answer is not just “call list objects once,” but “keep following pages until there are no more results.”

Use the AWS CLI for a Quick Listing

For simple inspection from the command line:

aws s3 ls s3://my-bucket --recursive

That is convenient for humans, but applications usually need to use the SDK or API directly.

Use Pagination in Code

In Python with Boto3, the usual answer is a paginator.

1import boto3
2
3s3 = boto3.client("s3")
4paginator = s3.get_paginator("list_objects_v2")
5
6for page in paginator.paginate(Bucket="my-bucket"):
7    for obj in page.get("Contents", []):
8        print(obj["Key"])

This is the correct scalable pattern because it keeps requesting additional pages until the bucket listing is complete.

Understand What “All Objects” Really Means

S3 listings can also be filtered by prefix, so make sure you know whether you want:

• every key in the bucket
• every key under a prefix
• only current versions versus a version-aware listing

The API shape matters if the bucket is large or versioned.

Common Pitfalls

• Calling the listing API once and assuming the bucket contents were complete.
• Forgetting that empty pages may need a safe fallback when Contents is absent.
• Confusing a prefix-scoped listing with a full-bucket listing.
• Using recursive CLI listing for automation when an SDK paginator would be more controllable.
• Assuming S3 “folders” are real directories instead of key prefixes.

Summary

• Large S3 bucket listings require pagination.
• The AWS CLI can list recursively for quick human use.
• SDK paginators are the normal answer for application code.
• Be clear about whether you want the whole bucket or only a prefix.
• In S3, object listing is fundamentally key-prefix traversal, not directory walking.