Minimal mime type implementation for use with the mail and rest-client gem.


Add this line to your application's Gemfile:

gem 'mini_mime'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mini_mime


require 'mini_mime'

# => "text/plain"

# => "txt"

# => false


MiniMime is optimised to minimize memory usage. It keeps a cache of 100 mime type lookups (and 100 misses). There are benchmarks in the bench directory

Memory stats for requiring mime/types/columnar
Total allocated: 9869358 bytes (109796 objects)
Total retained:  3138198 bytes (31165 objects)

Memory stats for requiring mini_mime
Total allocated: 58898 bytes (398 objects)
Total retained:  7784 bytes (62 objects)
Warming up --------------------------------------
cached content_type lookup MiniMime
                        52.136k i/100ms
content_type lookup Mime::Types
                        32.701k i/100ms
Calculating -------------------------------------
cached content_type lookup MiniMime
                        641.305k (± 3.2%) i/s -      3.232M in   5.045630s
content_type lookup Mime::Types
                        361.041k (± 1.5%) i/s -      1.831M in   5.073290s
Warming up --------------------------------------
uncached content_type lookup MiniMime
                         3.333k i/100ms
content_type lookup Mime::Types
                        33.177k i/100ms
Calculating -------------------------------------
uncached content_type lookup MiniMime
                         33.660k (± 1.7%) i/s -    169.983k in   5.051415s
content_type lookup Mime::Types
                        364.931k (± 2.8%) i/s -      1.825M in   5.004112s

As a general guideline, cached lookups are 2x faster than MIME::Types equivelent. Uncached lookups are 10x slower.


MiniMime uses the officially maintained list of mime types at mime-types-datarepo to build the internal database.

To update the database run:

bundle exec rake rebuild_db

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.