Kraken.io

Kraken.io optimises images through an API and a web interface, priced by the volume of image data processed each month rather than by image count. A testing quota is available without a credit card, which lets a developer establish whether the results are acceptable before any commitment.

Pricing by data volume rather than image count is the right unit for this work. Compressing a thumbnail and compressing a large photograph are very different amounts of processing, and a per image price either overcharges for small files or undercharges for large ones.

Being API first shapes who this suits. It is aimed at developers building optimisation into an application rather than site owners installing a plugin, which is a smaller audience but one that needs predictable behaviour and documented parameters more than it needs a friendly interface.

The published tiers start with a free allowance of five hundred megabytes of images per month, then Micro at five dollars a month or fifty dollars a year, and Basic at nine dollars a month, with additional data charged at five dollars per gigabyte beyond the plan allowance. Annual billing includes two months free, and the overage rate rather than the tier is what a variable workload should be budgeted against.