The easiest and recommended option is to use a randomly generated suffix. The auto-generated DOI strings use a-z, 0-9. They avoid i, l, o as they are easily mixed up with 0, 1. We group the suffix into blocks of 4, separated by a hyphen. You can generate a random suffix in both Fabrica and the API and your DOI will look something like this 10.5438/9te8-5h68.
If you choose not to use this option then remember:
The DOI suffix must be unique within each prefix. The optimum length of a DOI suffix is 6–10 characters.
Only use a-z (lowercase), 0-9 and - in a DOI suffix. Other characters might have special meaning or will be escaped.
Avoid human-readable information in a DOI suffix because any meaning may change over time. Further advice on DOI syntax:
Updated about a month ago