What Is an Image API? Five Kinds and What Each Does
The five kinds of image API, with a real request for each, what each one is priced on, and how to pick the ones your app needs.
Image Upload API Pricing for Uploads, Storage and Bandwidth
How image upload APIs price uploads, transformations, storage and bandwidth, with a worked monthly cost for a store with 2,000 products.
Key takeaways
- Image upload APIs charge on four meters: uploads, transformations, storage and bandwidth. A plan bundles an amount of each.
- Filestack’s plans, which run Image Upload API, go from Free at $0 to Scale at $379 a month, with custom Enterprise pricing.
- Bandwidth is the meter that fills first once images are live. In the worked example, a store with 2,000 products used 62.8 to 109.1 GB of the 75 GB included on the Start plan, depending on image format.
- A transformation URL counts once during its cache period, 30 days by default, however many times the image is viewed. Each view counts toward bandwidth.
- Serving AVIF instead of JPG cut the example store’s monthly bandwidth by 42% and kept it inside the Start plan.
What do image upload APIs charge for?
Image upload APIs charge for uploads, transformations, storage and bandwidth, and each plan includes a monthly amount of every one. Filestack’s pricing defines the four this way (Filestack pricing):
- Uploads: each file uploaded counts as one upload, and each file in a multi-file upload counts separately. The count resets every month.
- Transformations: a transformation counts when the stored file is modified, such as a resize, crop or format change. A URL that chains several tasks counts as one transformation during the cache period.
- Storage: a file uploaded to Filestack’s storage reduces the storage amount by its size.
- Bandwidth: bandwidth counts when a file is viewed or downloaded, and does not count for uploads.
Every upload returns a CDN URL, and transformations are tasks in that URL, so the meters follow what happens to an image: it is uploaded once, stored, transformed into the variants a page needs, and delivered on every view. You upload images through an API and all four meters are billed on one account.
Which meter grows fastest?
Bandwidth, because it grows with every page view. Uploads and storage grow with the number of photos, and transformations grow with the number of distinct variants.
In the worked example below, bandwidth reaches 84% to 145% of the Start plan’s allowance, while storage uses 3%, uploads 30% and transformations 60%.
What does a 2,000-product store use in a month?
A store with 2,000 products uses about 6,000 uploads, 1.3 GB of storage, 30,000 transformations and between 62.8 and 109.1 GB of bandwidth in a month, under the assumptions below. The photo sizes are the measurements from WebP vs AVIF vs JPG.
| Assumption | Value |
|---|---|
| Products and photos | 2,000 products, 3 photos each, 6,000 photos |
| Photo size | 209,870 bytes each, the test photo from the WebP vs AVIF vs JPG measurements |
| Variants per photo | 720 px for the product page in AVIF, WebP and JPG; the first photo of each product also at 480 px square and 240 × 300 in the three formats |
| Product page views | 60,000 a month, each loading one 720 px photo |
| Category page views | 40,000 a month, each loading 48 tiles at 480 px square |
| Caching | none, so every view downloads every file |
| Measured sizes | Filestack CDN responses, October 30, 2026 |
Uploads are 6,000, one per photo. Storage is 6,000 × 209,870 bytes, or 1.26 GB. Transformations are 6,000 × 3 formats for the product page plus 2,000 × 6 for the grid and cart variants, or 30,000. Bandwidth depends on the format served:
| Format served | Product pages | Category pages | Total | Share of 75 GB |
|---|---|---|---|---|
| JPG | 7.4 GB | 101.7 GB | 109.1 GB | 145% |
| WebP | 5.1 GB | 85.6 GB | 90.7 GB | 121% |
| AVIF | 3.1 GB | 59.7 GB | 62.8 GB | 84% |
A real store serves a mix, because the browser picks the first format it supports, so the bill lands between the rows.
How do resizing and WebP or AVIF lower the bill?
Resizing cuts bandwidth first and a modern format cuts it again, and both change the bandwidth meter and nothing else. A 721-pixel original shown in a 240-pixel cart slot sends about ten times the bytes the slot needs, as measured in the format comparison.
Moving the example store from JPG to AVIF removes 46.3 GB a month, 42% of its bandwidth. At the Start plan’s overage rate of $0.20 per GB, that is the difference between $75.82 and $69.00 a month: JPG exceeds the 75 GB allowance by 34.1 GB, WebP by 15.7 GB, and AVIF stays inside it.
Two habits keep the transformation count down. Keep the order of tasks in a URL the same on every page, because Filestack counts the same tasks in a different order as a new transformation. And reuse the same few sizes instead of one size per slot, since each distinct URL counts once per cache period.
This URL chains three tasks, rotation from EXIF data, a 480 px square crop and AVIF output, and counts as one transformation for its cache period:
https://cdn.filestackcontent.com/rotate=deg:exif/resize=width:480,height:480,fit:crop,align:center/output=format:avif,quality:60/zcjsVk1qSKWjIebIhHucIt returns a 31,108-byte AVIF, the AVIF tile size used in Table 2. Put resize before rotate on another page and the same image counts as a second transformation.
How do the plans compare?
Plans run from Free at $0 to Scale at $379 a month, and each includes a monthly amount of the four meters. These are the plans on the Filestack pricing page on November 4, 2026:
| Plan | Price | Uploads | Transformations | Bandwidth | Storage | Max file size |
|---|---|---|---|---|---|---|
| Free | $0 | 500 | 1,000 | 1 GB | 1 GB | 20 MB |
| Start | $69 a month | 20,000 | 50,000 | 75 GB | 50 GB | 1 GB |
| Grow | $199 a month | 50,000 | 150,000 | 200 GB | 150 GB | 2 GB |
| Scale | $379 a month | 125,000 | 300,000 | 400 GB | 350 GB | 5 GB |
| Enterprise | custom | custom | custom | custom | custom | custom |
Usage beyond a plan’s allowance is billed at overage rates, or you can move to the next plan. The rates fall as the plan rises:
| Meter | Start | Grow | Scale |
|---|---|---|---|
| Bandwidth, per GB | $0.20 | $0.15 | $0.10 |
| Uploads, each | $0.006 | $0.005 | $0.004 |
| Transformations, each | $0.0025 | $0.002 | $0.00125 |
| Storage, per GB | $0.50 | $0.375 | $0.25 |
The example store needs Start at minimum, because its 1.3 GB of storage and 6,000 uploads pass the Free allowances of 1 GB and 500.
Frequently asked questions
Do transformations count every time an image is viewed?
No. A transformation URL counts once during its cache period, which is 30 days by default, and each view after that counts toward bandwidth only. Changing the order of the tasks in the URL creates a new transformation.
What happens if I go over my plan’s bandwidth?
Usage above the allowance is billed at the plan’s overage rate, $0.20 per GB on Start, $0.15 on Grow and $0.10 on Scale. You can also upgrade to the next plan at any time.
Can I move to a higher plan later?
Yes. The pricing page states that you can upgrade to a higher plan at any time by contacting support, and Enterprise customers can negotiate custom overage rates.
Sources
- Filestack, Pricing and plans, including the overage rates, the usage counting FAQ and the cache period, checked November 4, 2026.
- File sizes: Filestack CDN measurements of one 209,870-byte photo, October 30, 2026, as described in WebP vs AVIF vs JPG.
- Monthly usage figures: our calculation from the assumptions in Table 1.
