Sqids (pronounced "squids") for Elixir is a library for generating YouTube-looking IDs from numbers. These IDs are short, can be generated with a custom alphabet and are collision-free. Read more.

This is what they look like in URLs:

https://example.com/LchsyE
https://example.com/Uxmq8Y
https://example.com/3CwlG7

The main purpose is visual: you can use Sqids if you'd like to expose integer identifiers in your software as alphanumeric strings.

• Link shortening: default alphabet is safe to use in URLs, and common profanity is avoided
• Event IDs: collision-free ID generation
• Database lookups: by decoding IDs back into numbers

• Sensitive data: this it not an encryption library
• User IDs generated in sequence, or equivalents, which can be decoded, revealing user count and/or business growth

• 🆔 Generate short IDs from non-negative integers
• 🤬 Avoid common profanity in generated IDs
• 🎲 IDs appear randomized when encoding incremental numbers
• 🧰 Decode IDs back into numbers
• ↔️ Generate IDs with a minimum length, making them more uniform
• 🔤 Generate IDs with a custom alphabet
• 👩‍💻 Available in multiple programming languages
• 👯‍♀️ Equally configured implementations produce the same IDs
• 🍻 Small library with a permissive license

The package can be installed by adding sqids to your list of dependencies in mix.exs:

def deps do
  [
    {:sqids, "~> 0.1.0"}
  ]
end

iex> {:ok, sqids} = Sqids.new()
iex> numbers = [1, 2, 3]
iex> id = Sqids.encode!(sqids, numbers)
iex> ^id = "86Rf07"
iex> ^numbers = Sqids.decode!(sqids, id)

Note 🚧 Because of the algorithm's design, multiple IDs can decode back into the same sequence of numbers. If it's important to your design that IDs are canonical, you have to re-encode decoded numbers and check that the generated ID matches.

Having to pass sqids context on every encode and decode call can be cumbersome.

To work around this, you can create context with new!/0 or new!/1 at compile time if all options are either default or known at that moment:

iex> defmodule MyApp.CompileTimeSqids do
iex>   import Sqids.Hacks, only: [dialyzed_ctx: 1]
iex>   @context Sqids.new!()
iex>
iex>   def encode!(numbers), do: Sqids.encode!(dialyzed_ctx(@context), numbers)
iex>   def decode!(id), do: Sqids.decode!(dialyzed_ctx(@context), id)
iex> end
iex>
iex> numbers = [1, 2, 3]
iex> id = MyApp.CompileTimeSqids.encode!(numbers)
iex> ^id = "86Rf07"
iex> ^numbers = MyApp.CompileTimeSqids.decode!(id)

This also allows you to encode and decode IDs without managing context.

If not all options are known at compile time but you'd still like to not pass context on every encode and decode call, you can use Sqids, which will generate functions that retrieve the underlying context transparently and call Sqids for you.

The context is stored in a uniquely named persistent_term, managed by a uniquely named process, which is to be placed under your application's supervision tree. Both names are derived from your module's.

iex> defmodule MyApp.SupervisedSqids do
iex>   use Sqids
iex>   # Functions encode/1, encode!/1, decode/1, decode!/1, etc
iex>   # will be generated.
iex>
iex>   @impl true
iex>   def child_spec() do
iex>       child_spec([
iex>           # alphabet: alphabet,     # Custom alphabet
iex>           # min_length: min_length, # Padding
iex>           # blocklist: blocklist    # Custom blocklist
iex>       ])
iex>   end
iex> end
iex>
iex>
iex> defmodule MyApp.Application do
iex>   # ...
iex>   def start(_type, _args) do
iex>      children = [
iex>        MyApp.SupervisedSqids,
iex>        # ...
iex>      ]
iex>
iex>      opts = [strategy: :one_for_one, name: MyApp.Supervisor]
iex>      Supervisor.start_link(children, opts)
iex>   end
iex> end
iex>
iex>
iex> {:ok, _} = MyApp.Application.start(:normal, [])
iex> numbers = [1, 2, 3]
iex> id = MyApp.SupervisedSqids.encode!(numbers)
iex> ^id = "86Rf07"
iex> ^numbers = MyApp.SupervisedSqids.decode!(id)

Examples of custom configuration follow. All options are applicable to the two convenient ways of creating context shown above.

Note that different options can be used together for further customization. Check the API reference for details.

iex> {:ok, sqids} = Sqids.new(min_length: 10)
iex> numbers = [1, 2, 3]
iex> id = Sqids.encode!(sqids, numbers)
iex> ^id = "86Rf07xd4z" # instead of "86Rf07"
iex> ^numbers = Sqids.decode!(sqids, id)

(Older IDs, for ex. generated with a previous configuration in which padding was not yet enforced or a different length was configured, can still be decoded.)

Generated IDs will only contain characters from the chosen alphabet, which is sensitive to both case and order.

iex> {:ok, sqids} = Sqids.new(alphabet: "cdefhjkmnprtvwxy2345689")
iex> numbers = [1, 2, 3]
iex> id = Sqids.encode!(sqids, numbers)
iex> ^id = "wc9xdr"
iex> ^numbers = Sqids.decode!(sqids, id)

In order to decode IDs back, they need to be in the same alphabet.

For practical reasons, the standard limits custom alphabets to ASCII characters.

(Thanks to @benjiwheeler for his suggestion for a set of unambiguous looking characters on Stack Overflow.)

As an example, set the ID generated with default options as the blocklist.

iex> {:ok, sqids} = Sqids.new(blocklist: ["86Rf07"])
iex> numbers = [1, 2, 3]
iex> id = Sqids.encode!(sqids, numbers)
iex> ^id = "se8ojk" # see how "86Rf07" was censored
iex> ^numbers = Sqids.decode!(sqids, id)

The API reference can be found on HexDocs.

MIT