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s3sup - static site uploader for Amazon S3

s3sup may be better than other S3 syncing solutions (e.g. s3sync) if you host a static site on S3. Main features include:

  • MIME type detection, with Content-Type set correctly for most files.
  • Fast and efficient synchronisation to S3 through maintaining a catalogue of content/metadata checksums for files already uploaded.
  • Hierarchical configuration of important HTTP headers (e.g. Cache-Control and Content-Disposition) on groups of files or individually.

Demo of new site being uploaded to S3:

Other features:

  • Ordering of uploads to prevent HTML files referencing static assets that haven't been uploaded yet.
  • Deletes files from S3 that no longer exist in the local project directory. This can also be prevented with --nodelete command line option or preserve_deleted_files config file key, should you want them to stick around.

Getting started

Follow these steps to get a new site uploaded to S3 with s3sup.

1) Add s3sup.toml file to your local static site root

Inside your local static site directory, add an s3sup configuration file for the first time using:

s3sup init

Then edit the skeleton configuration file created at ./s3sup.toml. For a guide to the configuration settings, see section below. To verify the destination path, HTTP headers and defaults that s3sup will set for an individual file, use:

s3sup inspect <filepath>

2) Configure AWS credentials

AWS credentials can be configured using any method that the underlying boto3 library supports. For most users, this will mean creating a credentials file at ~/.aws/credentials following this template:


Or alternatively credentials can be provided as environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY.

3) Run s3sup

Check what changes s3sup thinks needs to be made to S3. At the beginning, this will indicate that all files are new and need to be uploaded:

s3sup status

Then upload changes to S3:

s3sup push


s3sup can be installed using pip. Please note s3sup supports Python 3 only:

pip3 install s3sup

No distribution specific packages are available yet, please use the pip installation method or download source from GitHub.

To see the commands available, run s3sup with --help:

$ s3sup --help
Usage: s3sup [OPTIONS] COMMAND [ARGS]...

  s3sup - Amazon S3 static site uploader

  --help  Show this message and exit.

  init     Create a skeleton s3sup.toml in the current directory.
  inspect  Show calculated metadata for individual files.
  push     Synchronise local static site to S3.
  status   Show S3 changes that will be made on next push.

Each command also provides a --help:

$ s3sup push --help
Usage: s3sup push [OPTIONS]

  Synchronise local static site to S3.

  Use --dryrun to test behaviour without changes actually being made to S3.
  Or use "s3sup status".

  This command has two other aliases: upload or sync.

  -v, --verbose          Output more informational messages than normal.
  -p, --projectdir TEXT  Specify local s3sup static site directory (containing
                         s3sup.toml). By default the current directory is
  -n, --nodelete         Do not delete any files on S3, add/modify operations
                         only. Alternatively set "preserve_deleted_files" in
  -d, --dryrun           Simulate changes to be made. Do not modify files on
  --help                 Show this message and exit.

Configuration file guide

s3sup expects an s3sup.toml configuration file within the root directory of your static site. Only the [aws] section must be included at minimum:

Optional: Global configuration section

These settings must be placed at the top of the s3sup.toml file otherwise schema validation errors will occur (TOML interprets them as as belonging to the previous section otherwise):

Configuration key Required Default Type Expected value
preserve_deleted_files Optional false Boolean Setting to true will prevent files being deleted from S3 when they are deleted in the local project. This can be useful if your site has a long cache lifetime and you don't want cached pages to reference stylesheets/JavaScript files that suddenly disappear. This feature only prevents file deletions, it doesn't prevent file contents being overwritten if updated locally. This can also be achieved by supplying --nodelete as a command line option.
charset Optional 'utf-8' String Specify the character encoding of text files within this s3sup project. The charset is appended to Content-Type header. This can also be overriden on a [[path_specific]] basis.

Required: [aws] section

Configuration settings related to AWS:

Configuration key Required Default Type Expected value
region_name Required N/A String AWS region that the S3 bucket is located in. E.g. 'eu-west-1'.
s3_bucket_name Required N/A String Name of the S3 bucket. E.g. 'mywebsitebucketname'
s3_project_root Optional Bucket root String S3 sub path where the local project should be uploaded to, without a leading slash. E.g. 'staging/'. By default the local project is uploaded to the root of the S3 bucket.

Optional: One or more [[path_specific]] sections

One or more [[path_specific]] sections may be included. Each [[path_specific]] section must contain a path specification for which the directives in that section should apply to. The path can be the relative path to a file within the project directory, or a regular expression matching multiple paths.

If multiple [[path_specific]] entries match the same path, directives are combined from all matching [[path_specific]] entries, with the last matching [[path_specific]] directive entry in the configuration file winning for equivalent directive keys.

Along with path, the following directives can be set:

Configuration key Required Default Type Expected value
path Required N/A String Regular expression matching multiple relative paths, or an individual relative path to a file.
ACL Optional 'public-read' String S3 access permissions for the matching paths. One of: private, public-read, authenticated-read.
WebsiteRedirectLocation Optional None String Instead of serving the file when a client requests this path, instruct S3 to respond with a redirect to the specified URL instead. Note that URLs must be absolute, e.g. ''.
Cache-Control Optional max-age=10 String Set HTTP header value to control cache lifetime. A short default cache lifetime is set to provide basic origin shielding should an explicit one not be set.
Content-Disposition Optional None String Set HTTP header value to control whether the browser should display the file contents or provide a download dialog to the user
Content-Type Optional Automatic String Override Content-Type HTTP header value. Only override this if absolutely necessary as s3sup MIME type detection normally sets this header correctly.
charset Optional 'utf-8' String Manually specify the character encoding of text containing files. This is appended to Content-Type HTTP header. Usually setting charset in the global configuration section is adequate but this directives allows control on a path level.
Content-Encoding Optional Automatic String Set Content-Encoding HTTP header value. Only override this if absolutely necessary as s3sup detects encoding automatically. For wide browser support, it is recommended to store content uncompressed in S3 and then use dynamic gzip compression in a CDN layer.

Use s3sup inspect <filename> to check the attributes that s3sup will set based on your configuration settings and defaults.

Optional: [mimetype_overrides] section

Optional, usually not required. Provide manual mappings of file extensions to MIME type, which will take precedence over any automatic MIME type detection that s3sup has made. This can be useful for very modern MIME types E.g.

'.woff3' = 'font/woff3'
'.oml' = 'application/oml'

Example configuration file

The following example configuration:

  • Sets all files with a cache lifetime of two minutes by default.
  • Sets a longer cache lifetime on PDFs and a response header to trigger the browser to download the file rather than display it.

Example s3sup.toml:

region_name = 'eu-west-1'
s3_bucket_name = 'mys3websitebucket'

path = '^.*$'
Cache-Control = 'max-age=120'

path= '^/assets/download/[0-9]+.pdf$'
Content-Disposition = 'attachment'
Cache-Control = 'max-age=360'