Knockout API

Knockout API provides image and video processing through a browser app and API. Its image tools include background removal and replacement, batch processing, masking, smart crop, stickers, outlines, shadows, and inpainting. The API also handles image upscaling, portrait restoration, colorization, and object removal. Video background removal works asynchronously, with job polling to check progress. In the browser Canvas, users can make layered designs with text and effects, then save canvases and cutouts to a free account. Developers can connect through REST, any HTTP client, or official Node, React, Python, and CLI options. Knockout says it manages GPU processing, endpoint updates, usage records, credentials, teams, and billing. Its privacy policy says uploaded images are processed in GPU worker memory, are not kept after the response, and are not used for model training. Free usage is limited to 30 images per month and 60 requests per minute. The paid Pay-as-you-go plan is $0.02 a month, billed for metered usage.

Knockout API combines browser-based design with image and video processing endpoints, alongside several developer connection options. Check the free image and request limits against expected workload before choosing a plan.

The free tier is positioned for evaluation, side projects, and open-source work. Paid options may suit early startups, designers, agencies, power users, and production workloads, depending on usage needs.

Overview

Knockout API is a browser-based design and image-and-video processing service for developers who need creative operations in an application, and designers who want a Canvas alongside them. Its broad toolset makes it more than a background-removal endpoint, but the free image allowance is best treated as an evaluation cap, not a production quota.

Key features

Image operations span background removal and replacement, blur, foreground isolation, masking, smart crop, batch processing, stickers, outlines, shadows and inpainting. The API also offers upscaling, portrait restoration, colorization and object removal. That range is useful when an application needs several image workflows from one service; teams needing only a narrow, predictable operation may not benefit from the breadth.

Video background removal works asynchronously: an application submits a job and polls for completion, so it does not return a finished clip in the same immediate way as a synchronous image call. Knockout supports MP4, MOV, AVI, WebM and MKV, clips up to 30 minutes, exports up to 1080p, and transparent video output. The site says warm background-removal calls take around 200ms for a 1024×1024 image, while a first call after idle may take longer as capacity starts. That caveat matters in user-facing workflows where first-request delay is noticeable.

The browser Canvas handles layered compositions with text and effects; free accounts can save canvases and cutouts. Developers can connect through REST or any HTTP client, with official Node, React, Python and CLI options. Knockout says it handles GPU processing, endpoint updates, usage records, credentials, teams and billing, with GPU infrastructure powered by Modal. The privacy policy says uploads are processed in GPU worker memory, not retained after the response, and not used to train models. It also says API tokens are SHA-256 hashed, passwords use Supabase Auth with bcrypt, and traffic is encrypted via TLS. EU/EEA users have additional GDPR rights and can contact the company about them.

Pricing

Free costs nothing, has no expiring signup grant, and allows 30 images per month at 60 requests per minute. Community support and a small quota make it suitable for evaluation, side projects and open-source work, but 30 monthly images will constrain even modest recurring use.

Pay-as-you-go starts at $0.02 a month, with metered usage billed monthly. It includes all endpoints, email support and a 600-request-per-minute limit with no monthly cap; PSD export is an add-on, and video background removal costs $0.10/output second. This is the more flexible fit for side projects and early startups whose image volume varies, though video costs can rise with output duration.

Knockout Plus costs $10 a month, billed monthly, and includes 250 images per month. It is aimed at designers, agencies and power users; the larger fixed allowance is an upgrade over Free, but still places a ceiling on included monthly image work.

Volume has custom pricing and targets 100k+ images per month, with Slack support. It is the production-oriented tier for workloads well beyond Plus; teams should compare its quote and terms with their expected throughput. Free offers community support, Pay-as-you-go email support and Volume Slack support; Plus has no support channel stated.

Platforms

Knockout is available as an API and on the web. The API accommodates REST and standard HTTP clients, while official client options cover Node, React, Python and CLI.

Who it's for

Knockout fits developers building image or video processing into products, as well as designers who want a browser Canvas and saved assets. Free is suited to evaluation and small noncommercial projects; Pay-as-you-go fits early usage that needs endpoint access without a monthly image cap; Plus is for regular creative work within 250 included images; and Volume is aimed at high-throughput production. It is less compelling when a strict monthly budget for video output is essential or when asynchronous processing does not suit the workflow.

Pros and cons

• Pro: A wide mix of image operations, enhancement tools and asynchronous video removal can cover multiple workflows through one API.
• Pro: Browser Canvas features and official client options give designers and developers distinct ways to work with the service.
• Pro: The privacy policy describes in-memory image processing, no post-response storage or model training, and TLS-encrypted traffic.
• Con: Free is limited to 30 images monthly, making it a trial-scale allowance rather than a sustained workload plan.
• Con: Video removal is separately charged at $0.10/output second on Pay-as-you-go and completes asynchronously.
• Con: First background-removal requests after idle can take longer than the stated warm-call timing.

Alternatives

For image and video workflows, compare video background removal software, AI video background removers, green screen software and AI background removers. Developers evaluating request simulation rather than image processing can consider MockWebServer, a free Android test library for HTTP, HTTPS and HTTP/2 clients available from Maven Central, or Parasoft SOAtest, which offers tailored pricing based on business needs and a free trial. Microcks is a free, open-source, community-driven CNCF Incubating project. Mockfly offers a free Starter tier with 500 requests per day, one project, four endpoints and two responses per endpoint. Mockzilla has a free tier capped at 1K requests per month, 5 requests per second, one simulation and 10 MB of data transfer. Beeceptor is another freemium option with a $10 a month Individual plan. MockAPI provides a free plan with one project and two resources, or a $5 a month paid plan with 20 projects and 50 resources. Mockttp has a free Hobbyist tier for basic traffic viewing and rewriting, manual breakpoints and a built-in HTTP client. For the broader category, see API mocking tools.

Verdict

Knockout API is a strong fit for developers who need a broad image toolkit, optional video background removal and a browser Canvas in the same service. Its central advantage is coverage across creative operations and developer integrations; its main drawbacks are the restrictive Free quota and separately metered video. Start with Free to assess fit, move to Pay-as-you-go for flexible image volume, and look elsewhere if video cost predictability or immediate synchronous completion is essential.