OPML to HDR Converter
FileFlip converts OPML to HDR entirely inside your browser, using Pandoc, MuPDF and ImageMagick compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert an OPML file to HDR?#
- Drop your OPML file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to HDR and the conversion starts on its own. FileFlip downloads 79.9 MB of WebAssembly the first time and nothing after that, then runs Pandoc, MuPDF and ImageMagick on your own machine.
- Save the HDR file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting OPML to HDR lose quality?#
Yes, in the sense that text stops being text. Each OPML page is rendered to pixels and handed to HDR, so the result looks right and can no longer be selected, searched, or reflowed.
Is it safe to convert OPML files online?#
Yes, because nothing is uploaded. FileFlip converts OPML files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What OPML to HDR actually does to the file#
Converting OPML to HDR runs on Pandoc, MuPDF and ImageMagick, downloads 79.9 MB of WebAssembly the first time and nothing after that, renders each page to pixels, keeps page layout, and drops selectable text and transparency.
| Engine | Pandoc, MuPDF and ImageMagick |
|---|---|
| Conversion path | 3 steps: OPML → HTML → PNG → HDR |
| Downloaded to your browser | 79.9 MB, once, then cached by your browser |
| Quality | Text becomes pixels |
| You get back | One image per page, zipped when the source has several |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Selectable text | Dropped | The target format has nowhere to put it. |
| Page layout | Kept | Carried through into the converted file. |
| Transparency | Dropped | The target format has nowhere to put it. |
Worth knowing before you start:
- pages render at twice their point size in opaque RGB, roughly 144 DPI, with no transparency
- reflowable input is laid out on a fixed 595x842pt page at 11pt before anything else happens
- the file passes through HTML on the way, so anything HTML cannot express does not survive
What is an OPML file?#
An OPML file is an XML document made of nested outline elements, most often used to move a list of RSS and Atom feed subscriptions from one feed reader to another.
Use OPML to move a list of feed subscriptions between RSS readers, or to export a hierarchical outline from an outliner app.
Convert OPML into a document format like HTML or Markdown when the outline itself, not the feed subscriptions, needs to be read as a document.
What is an HDR file?#
An HDR file stores a high-dynamic-range raster image using Radiance's RGBE encoding, which packs red, green and blue mantissas with one shared exponent per pixel so a scene can hold a far wider range of brightness than a standard 8-bit image.
Reach for HDR when you need a compact high-dynamic-range environment map or lighting reference that most 3D tools and renderers can read without a plugin.
Convert HDR to OpenEXR when a VFX pipeline needs true floating-point precision, an alpha channel or multiple layers in one file, or convert it to JPEG or PNG once the image has been tone-mapped for a normal display.
OPML to HDR questions people ask#
What is an OPML file?
An OPML file is an XML document that stores a nested outline, most commonly a list of RSS and Atom feed subscriptions. Feed readers use it to export a subscription list from one app and import it into another.
What do I use an OPML file for?
The main use of an OPML file today is moving feed subscriptions between RSS readers like Feedly, Inoreader or NetNewsWire, so switching apps does not mean resubscribing to every feed by hand. UserLand Software originally designed OPML for general hierarchical outlines, not just feeds.
Can I edit an OPML file by hand?
Yes, an OPML file is plain XML text, so it opens and edits in any text editor. Each subscription or outline entry appears as an outline element with attributes like a title and, for feeds, the feed's URL.
What is an HDR file used for?
An HDR file most often stores an environment map or lighting reference for 3D rendering, since Radiance's RGBE encoding was built for the Radiance lighting-simulation software. Photographers also use the .hdr extension for panoramas merged from several exposures, before tone-mapping the result down to a normal image.