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1. Quick Start¶

The goal of this chapter is to upload a file to storage and read it back within ten minutes, without writing a single line of C++.

Installation¶

Copy the S3CompatibleStorageDemo/ folder into your project's Plugins/ directory.
Regenerate your project files and build.
Make sure the plugin is enabled: Edit → Plugins → Networking → S3 Compatible Storage.

Step 1. Connection¶

Project Settings → Plugins → S3 Compatible Storage

Start with the Provider field. It's the most important one: picking a provider immediately gives you the correct addressing style, and for some services a ready-made endpoint too. This is usually where the reason for "nothing works even though the keys are right" is hiding.

Provider	Endpoint URL	Region
Amazon S3	leave empty	your bucket's region
Cloudflare R2	`https://<account-id>.r2.cloudflarestorage.com`	`auto`
Backblaze B2	`https://s3.<region>.backblazeb2.com`	from the B2 console
Google Cloud Storage	leave empty	`auto`
MinIO	`http://host:9000`	any value, but it takes part in the signature
Wasabi, DigitalOcean Spaces	depends on the region	depends on the region

Fill in Default Bucket — it's what the test buttons and the subsystem use.

Amazon S3: don't type the regional endpoint by hand. Leave Endpoint URL empty and just set the region. The plugin resolves s3.<region>.amazonaws.com on its own, because s3.amazonaws.com only serves us-east-1.

Step 2. Keys¶

Scroll to the S3 Credentials (Editor Only) section and enter your Access Key ID and Secret Access Key.

This section is deliberately separate from the rest of the settings. It's stored in your personal EditorPerProjectUserSettings.ini, which lives under Saved/, is excluded from version control by the standard .gitignore, and never ends up in a packaged game. The main settings page has no fields for keys at all — and that's deliberate too: anything saved there would travel inside the build, in DefaultGame.ini.

For a packaged game, keys come from a completely different place — see Credentials.

Step 3. Verification¶

Four buttons sit at the top of the settings page:

Button	What it does
Test Connection	One real request: is the endpoint reachable, does the signature match, is the bucket readable
List Objects	Shows the bucket's contents
Run Round Trip Check	Uploads a test object, reads it back, verifies the bytes, and deletes it. Requires write access
Clear Report	Clears the report

The result appears in the Report field right below the buttons. If a check fails, the report includes not just the provider's error text but also a line suggesting what to change.

The buttons use the exact same code as the packaged game, so a green result here means the configuration actually works — not just that it's syntactically valid.

Step 4. Uploading a file from Blueprint¶

Event BeginPlay
   │
   ├─► Get S3 Subsystem
   │        │
   │        └─► Get Default S3 Client ──┐
   │                                     │
   └─────────────────────────────────────┴─► S3 Upload File
                                                  Bucket Name : my-bucket
                                                  Object Key  : saves/player.sav
                                                  Local File Path : Saved/SaveGames/player.sav
                                                  │
                                                  ├─ On Started  → save the Transfer to a variable
                                                  ├─ On Progress → update a ProgressBar
                                                  ├─ On Success  → Print String "Done"
                                                  └─ On Failure  → Print String (Get S3 Diagnostic Hint)

Get S3 Subsystem is a standard Unreal node: Get Game Instance Subsystem with the class set to S3 Subsystem. The subsystem creates a client from your settings, keeps it alive, and returns the same instance on every call.

About Local File Path. The value above is a relative path: the plugin expands it against the project root on its own (Saved/SaveGames/player.sav becomes, for example, C:/MyProject/Saved/SaveGames/player.sav), the same way in the editor and in a packaged game. A full absolute path such as C:/Users/You/Desktop/player.sav works just as well. What doesn't work is an asset path like /Game/... — that's a reference to an object in the Content Browser, not a file on disk. A full breakdown of every case, with an example for each platform, is in «File Path: Absolute or Relative».

What to do with the pins¶

On Started fires immediately, before any data has moved. It gives you a Transfer object — save it to a variable if you want to give the player a "Cancel" button or draw progress.
On Progress fires as bytes move. The struct has Percentage for a progress bar and bTotalKnown — while it's false, the overall size isn't known yet, so show an indeterminate indicator.
On Success and On Failure — exactly one of the two, always. So cleanup can be written in one place.

All pins fire on the game thread, so it's safe to touch actors and widgets from any of them.

Step 5. Reading it back¶

S3 Download File
   Bucket Name     : my-bucket
   Object Key      : saves/player.sav
   Local File Path : Saved/SaveGames/player-downloaded.sav
   │
   ├─ On Success → the file is already on disk
   └─ On Failure → show Get S3 Diagnostic Hint

The file is written to disk as data arrives, so memory usage doesn't depend on its size. The Data pin is empty on success — the bytes are in the file. If the download fails, the partially-written file is deleted: a half-file that looks like a successful download is worse than no file at all.

To get the data in memory instead — for a small JSON file, say — use S3 Download Bytes.

Common first-run obstacles¶

Symptom	Cause
`SignatureDoesNotMatch` on a non-Amazon service	Path Style Addressing is disabled. Pick your provider from the list, and it turns on by itself
`NoSuchBucket` on MinIO	MinIO doesn't create buckets automatically. Use the S3 Create Bucket node or the MinIO console
The node does nothing, no pins fire	The Client pin is empty. Take the client from the subsystem
403 on everything in the packaged game	The build has no keys — they were left in the editor-only settings. See Credentials
`Cannot read <path>` on `S3 Upload File`	There's no file at the path you gave it. For a relative path, that's `Saved/...` under the project root, not wherever your OS file explorer happens to be open — see «File Path»

Next: 2. Configuration