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API

Choose the Returned File Format in Image Creation Requests

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For OpenAI image-generation requests, start with PNG: it is the Image API default. Choose JPEG when latency matters and you do not need transparency; OpenAI’s guide says JPEG is faster than PNG, without quantifying the difference. Choose WebP when the receiving workflow supports it, especially for web delivery. For a transparent background in the Responses API image-generation tool, choose PNG or WebP—not JPEG.

One important distinction: a file format is not the same as the way an API returns or packages image data. GPT Image uses output_format to select PNG, JPEG, or WebP. DALL·E 2 and DALL·E 3 use response_format to select a URL or base64 JSON. OpenAI’s relevant documentation was accessed September 29, 2026; check the current reference for your model and endpoint before implementing a request.

Choose by what happens to the image next

The right format depends on the image’s destination, not on a universal ranking of PNG, JPEG, and WebP. First decide whether you need transparency, then consider latency, compression controls, and the capabilities of the system that will receive the file.

Need Practical choice What the documentation establishes
A default or a starting point when requirements are unclear PNG PNG is the documented default for the Image API and the Responses API image-generation tool. Compatibility still depends on the receiving application.
Lower latency, with no transparent background Consider JPEG The Image API guide says JPEG is faster than PNG. It does not provide a numerical benchmark or promise the same difference for every request.
A transparent background PNG or WebP The Responses API image-generation tool guide excludes JPEG for transparent output.
Web delivery Consider WebP if the consumer supports it WebP supports lossy and lossless compression and alpha transparency, and RFC 9649 describes it as optimized for fast transfer over networks. That does not guarantee a smaller file or universal compatibility.
A compression setting JPEG or WebP with output_compression The documented setting range is 0–100 and applies to supported GPT Image JPEG/WebP output, not PNG. The range is not a file-size or quality guarantee.

These are directions, not substitutes for checking the consumer. An application, image pipeline, or upload endpoint may support only some formats. Confirm that support before relying on a choice, especially when the file will pass through several systems.

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What each format choice means

PNG: the safe default when requirements are not yet clear

If you have no reason to choose another format, leaving the documented default in place is straightforward. PNG is also one of the supported choices for transparent output in the Responses API image-generation tool. Do not infer from the default that PNG is always the best choice for speed, file size, or every downstream application; the available evidence establishes the default, not a universal performance winner.

JPEG: consider it when latency matters and transparency does not

OpenAI’s Image Generation guide states: “Using jpeg is faster than png, so you should prioritize this format if latency is a concern.” Treat that as a qualitative recommendation from the guide, not as a benchmark. It gives no percentage, timing, or guarantee for a particular model, image, or network condition. The Responses API image-generation tool does not support JPEG with transparent backgrounds.

WebP: a candidate for a compatible web workflow

WebP can be useful when the system displaying or storing the image accepts it. RFC 9649 documents both lossy and lossless compression and alpha transparency, and describes WebP as optimized for transfer over networks such as websites. Those capabilities do not mean every WebP image will be smaller than its PNG or JPEG counterpart. Compare actual outputs in your own workflow if size is important, and verify support in the destination rather than assuming it.

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Keep file format separate from response format

Parameter names differ across OpenAI image API surfaces and model families. Mixing them up can lead to a request that asks for the wrong thing—or uses a parameter that the selected model does not support.

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  • output_format selects the image file format for GPT Image: png, jpeg, or webp.
  • response_format is documented for DALL·E 2 and DALL·E 3 and selects url or b64_json. The API reference says generated URLs are valid for 60 minutes.
  • The API reference says response_format is unsupported for GPT Image models, which return base64-encoded images.

In other words, output_format is about the image file type; response_format is about how a DALL·E response supplies the image. A URL-versus-base64 choice is not a request for JPEG-versus-PNG, and changing a response envelope does not itself select a file format.

Set the format for the API surface you are using

  1. Identify the model and endpoint. Do not copy a parameter from a different image API surface just because both generate images. The Image API guide and Responses API tool guide document different request contexts.
  2. Choose the output file type. For GPT Image, use the documented output_format option with png, jpeg, or webp. PNG is the default if you do not choose another supported format.
  3. Check transparency before choosing JPEG. For transparent output in the Responses API image-generation tool, select PNG or WebP. The guide says JPEG is not supported for that case.
  4. Set compression only where supported. The documented output_compression option is for GPT Image with JPEG or WebP and has a 0–100 range. Do not apply it to PNG or assume a particular number means a guaranteed file size.
  5. Handle the returned data according to the model family. GPT Image returns base64-encoded images according to the reference. For DALL·E 2 or DALL·E 3, consult the response_format behavior if you need a URL or base64 JSON; a generated URL is valid for 60 minutes.
  6. Test the receiving path. Confirm that your decoder, storage layer, upload target, browser, or other consumer accepts the selected file type and the way the API supplies it.

The documentation cited here names parameters and allowed values but does not provide a single request body that safely applies to every model and endpoint. Use the current endpoint reference for the exact request syntax rather than transplanting a code sample between API surfaces.

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Compression control: what 0–100 does and does not tell you

The API reference lists output_compression as a 0–100 compression-level setting for supported GPT Image JPEG or WebP output. The guide presents the setting as a way to customize output, but the documented range alone does not establish the resulting file size, visual quality, or the best value for a specific image. It is not a PNG setting.

If compression is important, evaluate the outputs that matter to your application: the delivered image, its appearance at the intended display size, and whether the recipient accepts it. Keep the format and the response-delivery mechanism distinct while doing so. A DALL·E URL or base64 setting is not a compression level.

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Common mistakes and how to recover

  • Requesting JPEG for transparency: In the Responses API image-generation tool, JPEG is not supported with transparent backgrounds. Change to PNG or WebP.
  • Sending response_format to GPT Image: The API reference says that parameter is unsupported for GPT Image. Use the model’s documented behavior instead: it returns base64-encoded images, and output_format is the file-format setting.
  • Using output_format as if it chose a hosted URL: It chooses PNG, JPEG, or WebP for GPT Image; it does not select URL versus base64 JSON. Check the DALL·E response_format behavior when using DALL·E 2 or DALL·E 3.
  • Applying compression to PNG: The documented compression option is limited to GPT Image JPEG or WebP. Remove it for PNG rather than assuming it controls PNG output.
  • Assuming a compression value guarantees a particular size: The 0–100 range is a parameter range, not a size promise. Inspect the actual output in your own pipeline.
  • Choosing WebP without checking the destination: WebP has capabilities suited to web delivery, but RFC 9649 does not establish that every application in your workflow accepts it. Verify support with the receiving system.
  • Expecting JPEG to be a fixed amount faster: The OpenAI guide makes a qualitative comparison with PNG but does not publish a number. Do not budget around an invented percentage or treat the statement as a benchmark for your exact workload.
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Performance, delivery, and cost considerations

The source documentation establishes one qualitative performance point: OpenAI says JPEG is faster than PNG and recommends prioritizing it when latency is a concern. It does not publish a measured difference in the cited guide, so a precise speed estimate cannot be derived from that statement. No numerical benchmark comparing formats for this workflow is established here.

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  • Full HD Video: Records 1080p video for travel clips, family moments, or simple vlogging
  • Memory Support: Works with Class 10 SD, SDHC, or SDXC cards up to 512GB
  • LCD Screen and Battery: 2.7in LCD screen and a rechargeable lithium-ion battery for on-the-go use

For delivery, WebP’s documented compression modes, transparency support, and network-transfer orientation make it a reasonable option to assess for a web destination. They do not ensure it will reduce file size for your particular image or be accepted by every consumer. Select based on both the generated file and the actual path through your systems.

The references cited here do not establish format-specific API prices or a cost advantage for one output format. Do not infer a billing difference from the compression setting or from JPEG’s qualitative latency statement; check the applicable model and current API pricing separately if cost is part of the decision.

Or skip the browser setup

ScreenshotNeo is a separate website screenshot API and MCP server, not an OpenAI image-generation endpoint and not a way to set an image-generation response format. If the task is capturing a web page rather than generating an image, its one-call request looks like this:

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curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webp

See the ScreenshotNeo documentation. It accepts cookie and consent banners like a visitor and removes 60+ known consent platforms, newsletter popups, and chat widgets before capture; each cleanup step can be turned off. Bot checks, blank pages, timeouts, failed loads, and cache hits cost nothing, with the page verdict and billing status in response headers. Its MCP server gives AI agents tools for screenshots, page information, and PDFs. The free plan includes 1,000 shots a month with no card; paid plans start at $5 for 3,000. Sign up free for 1,000 screenshots a month, with no card required.

How to keep the choice current

OpenAI’s cited Image Generation guide, Responses API image-generation tool guide, and API reference were accessed September 29, 2026. Parameter support and model behavior can change. Before shipping, confirm the current reference for the model and endpoint you actually call—particularly format options, transparency combinations, response behavior, and compression support. That check matters more than assuming a setting documented for one API surface carries over to another.

Quick Recap

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Kodak PIXPRO FZ45 Digital Camera, 16MP Point & Shoot (Black)
16MP Sensor: Captures detailed photos with a CMOS sensor for everyday shooting; Full HD Video: Records 1080p video for travel clips, family moments, or simple vlogging
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SaleBestseller No. 2
Kodak PIXPRO FZ55-BK 16MP CMOS Sensor Camera 5X Optical Zoom 28mm Wide
Kodak PIXPRO FZ55-BK 16MP CMOS Sensor Camera 5X Optical Zoom 28mm Wide
16MP Sensor: Captures detailed photos with a CMOS sensor for everyday shooting; Full HD Video: Records 1080p video for travel clips, family moments, or simple vlogging
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Bestseller No. 4
Kodak PIXPRO FZ55-RD 16MP Camera 5X Optical Zoom 28mm Wide Angle 1080p
Kodak PIXPRO FZ55-RD 16MP Camera 5X Optical Zoom 28mm Wide Angle 1080p
16MP Sensor: Captures detailed photos with a CMOS sensor for everyday shooting; Full HD Video: Records 1080p video for travel clips, family moments, or simple vlogging
$139.99

Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.

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