Every conversion tool has limits: a maximum file size, maximum image dimensions, a maximum number of pages or minutes, and a daily allowance. Limits can feel arbitrary when you hit one. In reality, each one exists for a reason, and there is almost always a simple way around it. This guide explains every kind of limit you might meet and what to do about it.
Where to find the limits
Every tool page shows its limits before you upload. The upload area also checks your file in your browser before anything is sent, so you find out immediately rather than after waiting for a large upload. The exact numbers are set by the site administrator and can change, so always check the tool page for the current values.
File size limits
Why they exist
Large files take longer to upload, process and store, and they use more memory during conversion. Limits keep the service fast and reliable for everyone.
Typical values
By default, image tools accept files up to around 25 MB, document tools up to around 100 MB, and audio transcription up to around 200 MB. The tool page shows the current limit.
What to do if your file is too big
- Images: resize the image in any photo app. Very large camera images often contain far more pixels than you need.
- Documents: split the document into parts, or remove large embedded images if they are not needed.
- Audio: export the recording at a lower bitrate or in a compressed format such as MP3, or split it into parts.
Image dimension limits
Why they exist
Images are decoded into memory as raw pixels before conversion. A file that is small on disk can expand enormously in memory if it has huge dimensions. Limits on width, height and total pixels protect against these "decompression bombs" and keep conversions fast.
What to do
Resize the image to a more typical size. By default, images up to around 12,000 pixels on a side and 50 megapixels are accepted, which covers almost every camera.
Animation limits
Animated GIF and WebP files have limits on the number of frames and total animation length. Very long animations are better handled as video. Trim the animation or reduce the frame rate in an editor if you hit these limits.
Page limits for documents
EPUB to PDF estimates how many pages your book will produce at the chosen text size and checks it against a page limit. PDF tools check the number of pages in your PDF. If a document is too long, convert it in sections. For EPUB to PDF, a slightly smaller text size also reduces the page count.
Duration limits for transcription
Audio to PDF and Audio to EPUB accept recordings up to a few hours long by default. Longer recordings take longer to process and are more likely to contain long silences or interruptions. Split very long recordings into parts, for example one file per session of a conference.
Text length limits for narration
PDF to Audio and EPUB to Audio limit how much text can be read aloud in one conversion, roughly several hours of audio. The upload check estimates the listening time before you start. For long books, convert in parts, such as a few chapters at a time.
Daily allowances
Why they exist
Some conversions, particularly speech recognition and narration, rely on external services with real costs, and all conversions use shared computing resources. Daily allowances keep the service fair and sustainable for everyone.
How they work
Each tool has a daily allowance, and there is also an overall daily total. By default, signed-in users get substantially higher allowances than guests. Allowances reset each day. The tool page shows your allowance, and if you reach it, the message tells you clearly.
What to do
Create a free account for higher allowances, or come back the next day.
Other checks you might see
- "This file is not really a PNG" or similar: the file's contents do not match its name. Choose the tool for its real format.
- "This PDF looks scanned": the PDF contains images of pages, not text.
- "This e-book is DRM-protected": the book's content is encrypted and cannot be converted.
- "Too many requests": you made many requests quickly. Wait a moment and try again; the message tells you how long.
A worked example: a huge camera photo
A photographer tries to convert a 60 MB RAW-derived TIFF exported at 9,000 by 6,000 pixels. The image tool rejects it as too large. She exports a JPG at full size, which is much smaller, then converts that. If she only needs a web image, she resizes to 2,000 pixels first.
A worked example: a conference recording
A five-hour conference recording is over the duration limit for transcription. The organiser splits it into one file per session using a free audio editor, then transcribes each session separately, which also produces more manageable transcripts.
A worked example: a long textbook
A student wants a 700-page textbook as audio. The upload check estimates far more listening time than the limit. She converts it chapter by chapter, which suits her study plan anyway.
Questions people ask
Why does my small file fail the dimension check? It may be highly compressed but have very large pixel dimensions.
Do limits differ for signed-in users? Daily allowances are higher for signed-in users. File limits are the same for everyone.
Can limits change? Yes. Administrators may adjust them; the tool page always shows current values.
Why check in the browser first? It saves you from waiting for an upload that would be rejected anyway.
In short
Limits on file size, dimensions, frames, pages, duration, text length and daily usage keep the service fast, fair and safe. Check the tool page for current values, resize images, split long documents and recordings, and sign in for higher daily allowances. When you do hit a limit, the message tells you exactly which one and why.