Our reading tools work on files that are in a standard format. When one refuses to open, the reason is usually the format, the file size or something unusual inside the file. Here is what each tool accepts.
What each tool opens
- Dark PDF Reader: PDF files.
- EPUB Reader: EPUB 2 and EPUB 3 books that are free of DRM.
- DOCX Reader: standard .docx files. Older .doc files, password-protected documents and files that are not valid .docx packages cannot be opened.
- CSV / Excel Viewer: .csv and .xlsx files.
- Text Reader: pasted text, and .txt, .md and .html files.
- Image Color and Dark Screenshots: JPG, PNG and WebP images (Image Color also opens GIF files, using the first frame).
Common causes and fixes
The file has a different extension
If a Word file is saved as .doc, open it in Word or another editor and save it again as .docx. For spreadsheets, save or export as .xlsx or .csv.
The book is protected by DRM
Books bought from some stores are locked to a particular reading app. The EPUB Reader cannot open them. DRM-free EPUB files from other sources work.
Special characters look wrong in a CSV
Most UTF-8 files open without problems. If accents or other characters appear as strange symbols, export the CSV again as UTF-8 from your spreadsheet program and reopen it.
The PDF is protected or scanned
A PDF that needs a password may not open until the protection is removed in the program that created it. A scanned PDF opens, but its pages are pictures, so search cannot find words inside them.
The file is in the wrong tool
Each tool reads its own formats. A .xlsx file will not open in the Text Reader, and an EPUB will not open in the PDF reader. Check the list above and pick the tool that matches the file.
The file opens but looks empty
This can happen with a spreadsheet whose data sits on a different sheet, or a document that is mostly images. Look for sheet tabs in the viewer, and try opening the file in its usual program to see what it should contain.
The file is very large
The tools work inside your browser tab, so a very large file needs more memory. It may take longer to open, particularly on an older phone. Close other tabs, reload the page and try again.
Screen capture is blocked
In Dark Screenshots, the Capture screen button depends on your browser and device allowing screen sharing. If it does not, open an image file instead.
General steps
- Reload the page and try the file again.
- Try another browser, such as Chrome or Edge, to see if the problem follows the file.
- Open the file in its usual application. If it fails there too, the file may be damaged.
If a file opens everywhere except here, send us the file type and what you see through the contact form. Please do not attach private documents.