Image to PDF
Why does Image to PDF reject my images?
Read the error before changing your images. Image to PDF checks format and decoding, a 20-image maximum, 50 MiB of combined input, 20 megapixels per image and 80 megapixels combined. A rejected selection adds none of its files. Reduce the quantity, bytes or dimensions named by the error, then retry; a later build failure may need fewer or smaller images even within those limits.
Identify whether selection or building failed
There are two different failure points. During selection, the app checks incoming files before adding them to the lineup. If that check fails, the status says that no images from that selection were added and that the existing lineup is unchanged. Start with the error rather than clearing everything.
A failure after selecting Build PDF follows a different path: the error begins with Could not build PDF, and the status suggests fewer or smaller images. Accepted input has passed the selection checks, but that does not guarantee that the browser can finish constructing the document. Use the matching recovery steps below.
For a format error, export a real JPEG or PNG
The app examines file signatures, not just the filename extension. Renaming a HEIC file to holiday.jpg does not turn it into supported JPEG data. Export the image as JPEG or PNG in another tool, then choose the exported file. There is no built-in conversion step for unsupported input.
A recognized signature is only the first check. The browser must also decode the image. If the error says image cannot be decoded, follow its suggestion to export the image again. When several files were selected together, retry the supported files without the problem file; even files checked successfully earlier in that rejected selection were not added.
Separate image count from combined file size
The 20-image ceiling includes the current lineup and the new selection. If 18 pages are already loaded, choosing three more exceeds the ceiling. Add only two, remove an unwanted existing page, or prepare separate documents. Adding files in several selections does not create a fresh allowance.
The 50 MiB check also combines existing and incoming input files. It limits their source bytes, not the size of the finished PDF. For example, images totaling 48 MiB cannot accept another 3 MiB image. Reduce the input total or use fewer files. The app re-encodes images during building, so passing this check does not promise a PDF below 50 MiB.
For a pixel error, reduce image dimensions
Pixel limits measure decoded width multiplied by height. Each image can contain at most 20 million pixels, and the lineup can contain at most 80 million in total. A 6000 by 4000 image contains 24 million pixels and exceeds the individual limit, even if its compressed file occupies only a few MiB.
The combined limit can reject individually acceptable images. Five images measuring 5000 by 4000 each total 100 million pixels. Four total 80 million, meeting the pixel ceiling provided the other checks also pass. Existing pages count toward that total too.
Resize the source to smaller pixel dimensions in another tool before trying again. Lowering JPEG quality without changing width and height may reduce bytes, but it does not reduce this pixel calculation. Check both dimensions and file size when preparing replacements.
If building fails, retry a smaller document
The limits are guardrails, not a device-memory guarantee. Building decodes the accepted images and re-encodes them as JPEG on a white canvas. A selection can therefore be accepted yet still fail during the later build. The app has no setting to raise its limits or choose a lower encoding quality.
Follow the build status: remove some pages or prepare smaller versions, then select Build PDF again. For a large collection, make separate smaller documents and save each useful result. If you resize a source file outside the app, remove its old page and choose the replacement; the lineup does not automatically reload that external edit. Check the replacement page order before rebuilding.
AI-assisted ForgeHub editorial. App capabilities were checked against its implementation; this guide is not an independent review.
Frequently asked questions
Does choosing files one at a time bypass the limits?
No. Count, combined input bytes and combined pixels include images already in the lineup. Smaller selections can help isolate a troublesome file, but they do not reset the allowances.
Will reducing JPEG quality fix a megapixel error?
Not if the dimensions stay the same. Pixel count is width multiplied by height. Resize the image to fewer pixels; reducing encoded bytes addresses the separate input-size limit.
Can I raise the 20-image or 50 MiB ceiling?
The implemented limits are fixed, with no user control to increase them. Remove pages or prepare separate PDFs, and reduce source dimensions or file sizes as required by the error.
Why can an accepted image still fail during Build PDF?
Selection validates format, decoding and input limits. Building performs additional decoding and JPEG encoding and constructs the PDF. The guardrails do not guarantee enough device memory; follow the suggestion to use fewer or smaller images and build again.