# Export files to Amazon S3
Robot: `/s3/store`
🤖/s3/store exports encoding results to Amazon S3.
If you are new to Amazon S3, see our tutorial on [using your own S3 bucket](/docs/faq/how-to-set-up-an-amazon-s3-bucket.md).
The URL to the result file in your S3 bucket will be returned in the Assembly Status JSON. A returned URL does not make a private object public or grant read access. If your S3 bucket has versioning enabled, the version ID of the file will be returned within `meta.version_id`.
> [!Warning]
> **Configure private buckets explicitly.** The Robot’s default `acl` is still `"public-read"`. For a private bucket, set `acl: "bucket-default"` and do not supply ACL or grant headers. This omits the generated ACL header and works with [Bucket owner enforced Object Ownership](https://docs.aws.amazon.com/AmazonS3/latest/userguide/about-object-ownership.html), where ACLs are disabled. Keep S3 Block Public Access enabled. Setting `acl: "private"` still sends an ACL and is not equivalent to omitting it.
> [!Warning]
> **Use DNS-compliant bucket names.** Follow AWS’s [bucket naming rules](https://docs.aws.amazon.com/AmazonS3/latest/userguide/bucketnamingrules.html). The `url_prefix` parameter changes returned URLs; it does not change the bucket or its access permissions.
## Limit access
Use a dedicated AWS identity with access limited to the destination bucket and object prefix. Do not use [AWS root access keys](https://docs.aws.amazon.com/IAM/latest/UserGuide/root-user-best-practices.html). Store its access key ID, secret access key, bucket name and region as `key`, `secret`, `bucket` and `bucket_region` in Template Credentials, then reference their name with `credentials`. Trusted backend integrations can instead supply those parameters directly; do not expose AWS secrets in browser instructions.
The following is an [identity-based IAM policy](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_principal.html), attached to that dedicated identity, not a bucket policy. It intentionally has no `Principal`. Replace `{BUCKET_NAME}` and use a Robot `path` beginning with `uploads/`, or adapt both the policy prefix and the path together.
This example covers uploads and failed multipart-upload cleanup with an explicit `bucket_region`, `acl: "bucket-default"`, no ACL/grant headers, no tags and S3-managed encryption (SSE-S3). Existing bucket policies, organization controls or endpoint policies can still deny access.
```json
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "UploadAndAbortWithinPrefix",
"Effect": "Allow",
"Action": ["s3:PutObject", "s3:AbortMultipartUpload"],
"Resource": "arn:aws:s3:::{BUCKET_NAME}/uploads/*"
}
]
}
```
The uploader uses either `PutObject` or `CreateMultipartUpload`, `UploadPart` and `CompleteMultipartUpload`; failed multipart uploads can trigger `AbortMultipartUpload`. AWS maps the successful upload operations to `s3:PutObject`. Write access can **overwrite an existing object key**; it is not add-only. Choose unique object paths and consider versioning for recovery.
Add permissions only for features you use, following AWS’s [operation permission reference](https://docs.aws.amazon.com/AmazonS3/latest/userguide/using-with-s3-policy-actions.html):
* Without an explicit `bucket_region`, region discovery can require `s3:GetBucketLocation` and fallback `s3:ListBucket` on the bucket ARN, `arn:aws:s3:::{BUCKET_NAME}`, without an object suffix. Supplying the correct region avoids these discovery requests.
* ACL or grant headers require `s3:PutObjectAcl`; tags require `s3:PutObjectTagging` on the allowed object prefix. `bucket-default` does not remove ACL/grant headers you supply in `headers`.
* Downloading private results requires separate read authorization. Even a URL generated with `sign_urls_for` needs the signing identity to have the appropriate read permissions.
S3 applies its [bucket encryption configuration](https://docs.aws.amazon.com/AmazonS3/latest/userguide/default-bucket-encryption.html) when no encryption override is sent. You can request SSE-KMS through `headers`, using `x-amz-server-side-encryption: aws:kms` and `x-amz-server-side-encryption-aws-kms-key-id`. When either bucket default encryption or request headers select [SSE-KMS](https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingKMSEncryption.html), the uploading identity needs `kms:GenerateDataKey` on the relevant key, plus `kms:Decrypt` for multipart uploads. For a customer-managed key, grant these permissions with a compatible KMS key policy; the base S3 policy above does not include them. Do not add blanket `kms:*` or `sts:*` grants.
Short-lived AWS credentials are a matching set of `key`, `secret` and `session_token`. Have a trusted backend obtain and refresh all three, then supply them together when it creates the Assembly. It can pass them directly in Robot instructions or save and update them together through the [Template Credentials API](/docs/api/template-credentials-post.md). Keep all three out of browser instructions; replacing only the session token does not refresh expired access keys. This Robot passes the supplied credentials to S3; it does not assume a role or refresh expired credentials. Keep temporary credentials valid for the upload.
> [!WARNING]
> **Keep your credentials safe**
>
> Since you need to provide credentials to this Robot, always use this together with Templates and/or Template Credentials, so that you can never leak any secrets while transmitting your Assembly Instructions.
Stage: ga
## Usage example
Export uploaded files to `my_target_folder` in an S3 bucket:
```json
{
"steps": {
"exported": {
"credentials": "YOUR_AWS_CREDENTIALS",
"path": "my_target_folder/${unique_prefix}/${file.url_name}",
"robot": "/s3/store",
"use": ":original"
}
}
}
```
## Parameters
### `interpolate`
Controls whether Assembly Variables are interpolated for individual instruction fields.
By default, most Robot instruction fields interpolate Assembly Variables. Set this to `false` to treat every instruction field as literal text, or set an individual field path to `false` to treat only that field as literal text. For Robot-specific fields that are literal by default, set this to `true` or set that field path to `true` to opt back into interpolation.
Use field names such as `path`, or dotted paths such as `ffmpeg.vf` for nested objects.
Type: `boolean | Record`
### `output_meta`
Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast.
For images, you can add `"has_transparency": true` in this object to extract if the image contains transparent parts and `"dominant_colors": true` to extract an array of hexadecimal color codes from the image.
For images, you can also add `"blurhash": true` to extract a [BlurHash](https://blurha.sh) string — a compact representation of a placeholder for the image, useful for showing a blurred preview while the full image loads.
For images, `"thumbhash": true` instead extracts a base64-encoded [ThumbHash](https://evanw.github.io/thumbhash/) into `meta.thumbhash`, together with `meta.has_alpha` (whether an alpha channel exists, even when fully opaque). It describes EXIF-oriented pixels and uses the first frame of animated images. Extraction is best-effort: images above 40 megapixels, unsupported formats, or a failed/bounded decode produce no placeholder. Successful extraction adds a metadata charge equivalent to 20% of that file's bytes. No ThumbHash surcharge applies when disabled or when no hash is produced.
Set this option on the Step producing the image, such as `/upload/handle` for uploaded originals or `/image/resize` for processed outputs. Setting it only on `/transloadit/store` does not request extraction: storage preserves the producer's metadata. Transloadit Storage persists a generated hash with its immutable version and returns it in stored results and native asset reads. Direct S3 uploads do not generate placeholders. A placeholder contains image information, so protect it with the same access controls as the full image.
For videos, you can add the `"colorspace": true` parameter to extract the colorspace of the output video.
For videos, you can also add `"interlaced": true` to detect whether the video is interlaced. This combines the cheap ffprobe `field_order` flag with a bounded `idet` sampling pass over the first frames of the source, exposing `interlaced`, `field_order`, and a diagnostic `interlace_detection` object under `file.meta`. This is computationally expensive and billed accordingly.
For audio, you can add `"mean_volume": true` to get a single value representing the mean average volume of the audio file.
You can also set this to `false` to skip metadata extraction and speed up transcoding.
Type: `Record | boolean | Array`
### `user_meta`
Adds custom JSON metadata to each emitted file without changing its contents. Nested objects and arrays are supported.
Inheritance depends on the Robot. Values merge with existing `user_meta` on the output file; the current Step replaces matching top-level keys. Assign required keys explicitly when a Robot creates fresh outputs.
In processing Steps, `${file.*}` refers to the first input and `${result.*}` to the emitted file. Values are evaluated per output after the Robot runs, before subsequent metadata extraction and temporary storage. On `:original`, values are evaluated per upload before metadata extraction.
Downstream Steps read `${file.user_meta.key}`. See [Custom metadata](https://transloadit.com/docs/topics/assembly-variables.md#user-meta) for a complete example and inheritance rules.
Type: `Record`
Default: `{}`
### `result`
Whether the results of this Step should be present in the Assembly Status JSON
Type: `boolean`
Default: `false`
### `queue`
Setting the queue to 'batch', manually downgrades the priority of jobs for this step to avoid consuming Priority job slots for jobs that don't need zero queue waiting times
Type: `batch`
### `force_accept`
Force a Robot to accept a file type it would have ignored.
By default, Robots ignore files they are not familiar with.
[🤖/video/encode](/docs/robots/video-encode.md), for
example, will happily ignore input images.
With the `force_accept` parameter set to `true`, you can force Robots to accept all files thrown at them.
This will typically lead to errors and should only be used for debugging or combatting edge cases.
Type: `boolean`
Default: `false`
### `ignore_errors`
Ignore errors during specific phases of processing.
Setting this to `["meta"]` will cause the Robot to ignore errors during metadata extraction.
Setting this to `["execute"]` will cause the Robot to ignore errors during the main execution phase.
Setting this to `true` is equivalent to `["meta", "execute"]` and will ignore errors in both phases.
Type: `boolean | Array`
Default: `[]`
### `use`
Specifies which Step(s) to use as input.
* You can pick any names for Steps except `":original"` (reserved for user uploads handled by Transloadit)
* You can provide several Steps as input with arrays:
```json
{
"use": [
":original",
"encoded",
"resized"
]
}
```
* You can also tag input Steps with `as` to pass semantic intent to robots:
```json
{
"use": [
{
"name": ":original",
"as": "image"
},
{
"name": ":original",
"as": "mask"
}
]
}
```
> [!Tip]
> That's likely all you need to know about `use`, but you can view [Advanced use cases](/docs/topics/use-parameter.md).
Type: `string | Array | Array