Supported File Types for Online Faxing

PerPageFax accepts PDF, PNG, JPG, HEIC, and TIFF files up to 20 MB total and 100 pages per fax. Those are the rules that matter first, because a file can be supported and still fail if it crosses either limit.

If you're trying to send a contract, a scan, or a phone photo right now, the question isn't just what the file is called. It's whether that file will stay readable, fit the size cap, and make it through without a conversion headache.

Supported File Types at a Glance

PerPageFax keeps the format list simple on purpose. It accepts PDF for printable documents, PNG for lossless screenshots and scans, JPG for compressed photos, HEIC for iPhone and iPad captures, and TIFF for high-resolution reproductions.

Those five file types sit under two hard limits, a 20 MB total fax size cap and a 100-page per fax cap. Both limits apply to the whole fax job, not to each file by itself, so a stack of small uploads can still fail if the combined total is too large or too long.

Practical rule: supported file types tell you what the system can read, but the size and page limits tell you what it can actually send.

That difference matters more than people expect. A PDF can be perfectly valid and still be too large. A phone photo can be accepted and still produce a weak-looking fax if the image quality is poor.

The safest way to think about supported file types is this. PDF is the document-first option, while PNG, JPG, HEIC, and TIFF are image-first options that happen to work in a fax workflow. The rest of this guide focuses on what each type does well, where it causes friction, and how to choose the right one before you upload.

Document and Image Categories

The easiest way to understand supported file types is to split them into two buckets. PDF is the document container, while PNG, JPG, HEIC, and TIFF are raster image formats.

A PDF keeps more than a picture of a page. It can preserve selectable text, embedded fonts, vector shapes, and a fixed page order. That's why contracts, application forms, and multi-page reports usually travel more predictably as PDF than as a stack of image files.

Raster images work differently. They store a page as pixels, so the fax server sends what it receives, including any blur, compression, or cropping problems baked into the file. Text inside an image is no longer text, it's just part of the picture.

That split explains most compatibility confusion. A document exported as PDF usually preserves layout better. A photo saved as HEIC may look fine on your phone, but once it's rendered through a fax path, the image quality and viewer support can matter more than the original capture.

Simple rule: if the page has text you care about, start with PDF. If the page is fundamentally a photo or screenshot, choose an image format that keeps the picture readable.

This is also why fax systems often accept both document and image formats. Real workflows mix office files, scans, screenshots, and phone photos. The supported file types list has to cover all of them, not just one ideal format.

PDF, PNG, JPG, HEIC, and TIFF

PDF

Use PDF for contracts, signed forms, and anything that started life as a typed document. It keeps the page layout stable, which helps when the recipient needs to read signatures, paragraphs, and page breaks exactly as you sent them.

PDF also works well when you re-upload a downloaded application or an agreement you already signed. The file stays closer to the source document than a screenshot would. If the PDF is password-protected, remove the password first so the fax system can read it without friction.

PNG

Use PNG when you need clean edges and text fidelity, especially for screenshots, forms with sharp lines, and scans where legibility matters more than file size. PNG avoids the compression artifacts that can show up in JPG, so it's useful when the content includes small text or crisp graphics.

The tradeoff is size. A PNG can get large fast, so it deserves extra attention when you're close to the 20 MB ceiling. That matters most if you're combining several page images into one fax job.

JPG

Use JPG for photos, especially when the page is a photographed receipt, ID, or a color image that doesn't depend on perfect edge sharpness. JPG compresses well, which makes it easier to stay under upload limits.

The downside is visible softness if the image has a lot of small text. A JPG can be perfectly acceptable for a photo-driven page and still be a poor choice for a dense form.

HEIC

Use HEIC when the file came straight from an iPhone or iPad and you want to avoid a conversion step before upload. That convenience is helpful for mobile users who just captured a document or screenshot.

The caveat is compatibility outside the sender's device. HEIC can be less predictable in older viewers and mixed recipient environments, so it's smart to convert when the fax is time-sensitive or the destination is strict.

TIFF

Use TIFF for high-resolution scans, archived packets, and pages that need strong reproduction quality. TIFF is common in scanning and records workflows because it handles detailed page images well.

The tradeoff is footprint. TIFF files can become large quickly, so they're useful when fidelity matters more than compact size. That's why they're common in serious scan workflows, but not always the easiest choice for routine faxing.

For a practical walkthrough of document handling on Apple devices, see this iPhone PDF guide.

HEIC Files from iPhones and iPads

HEIC is the default photo format on many iPhones and iPads, and that makes it a common source file for mobile faxing. PerPageFax accepts HEIC directly, so an iPhone user doesn't have to convert every photo before upload.

That convenience matters most when the file is a fresh photo of a form, receipt, or handwritten page. If the image is already clear and the recipient workflow is simple, direct HEIC upload can save a step.

The catch is that not every environment treats HEIC the same way. Some Windows viewers and older tools still handle it less reliably, so conversion to PDF or JPG remains the safer path when the document is time-sensitive or going to a strict destination.

A good conversion option is the iPhone Photos app. Open the image, use Share, choose Print, pinch to zoom on the preview, then save or share the result as a PDF. Another option is to export a compatible copy from the Files app or to save the image as JPG when you want broader viewing support.

Practical rule: keep HEIC when convenience matters, convert when certainty matters.

HEIC support is useful because it reduces friction for mobile users. But the safest fax file is still the one the receiver can open, render, and read without needing any special handling.

Fax Size and Page Limits

PerPageFax uses two hard limits on every transmission, a 20 MB total upload cap and a 100-page maximum. Those numbers apply to the whole fax job, not to each file in isolation.

That distinction trips people up. Five files that are each small on their own can still fail together if their combined size crosses the limit. The same is true for page count, since the renderer counts the fax as a single submission.

High-resolution scans are the fastest way to hit the size ceiling. When images are detailed, even a small set of pages can become heavy after conversion. Lowering resolution, reducing color, or choosing PDF instead of raw images often keeps the submission within range.

A simple preflight check helps. Open the files, add up the total size, count the pages, and confirm that the final fax still fits both limits before you upload. If either number is too high, split the document or reduce the file size before you send.

Uploading from Desktop and Mobile Devices

Desktop uploads usually start with a file that already exists. You drag a PDF, TIFF, or downloaded document from Finder, File Explorer, or a browser folder into the upload area, which is a clean path when the source is already digital.

Mobile uploads begin differently. You often start from the camera roll, the iOS or Android share sheet, or the phone camera itself. That works well when the page is a photo, a screenshot, or a freshly captured form.

A phone camera can act like a portable scanner, but the capture quality depends on how the page is shot. Keep the device flat, use good light, and make sure the text is in focus before you upload. Otherwise, the fax may technically send but still arrive hard to read.

Desktop workflows are usually easier to control because the file is already exported, scanned, or downloaded. Mobile workflows are more flexible, but they need more attention to alignment and contrast. The upload flow itself may look similar, yet the source device changes the quality of the file before faxing even begins.

For a complete sending walkthrough, visit this online fax guide.

Choosing a Format for Legible Faxes

The file type should match the material, not just the device that created it. A typed contract should usually stay a PDF, while a photographed page from a phone often works better as PNG or JPG if you want straightforward compatibility.

A scanned archive or a page that needs strong detail can justify TIFF, especially when the document is already image-based and quality matters more than compact size. HEIC is convenient for capture, but it's not always the safest final format if the destination is strict or the deadline is tight.

Match the format to the content

• Typed or generated documents: Start with PDF, because it preserves page order and layout.
• Photographed pages: Use PNG or JPG, because the file is already an image and the upload path stays simple.
• Archived scans or detail-heavy records: Use TIFF when fidelity matters more than file size.
• iPhone captures: Keep HEIC only when the destination can handle it comfortably, otherwise convert first.

A fax can still fail to read clearly even when the extension is supported. Orientation, margins, contrast, and page order all shape the final result. A sideways page or a dim photo can look acceptable on a phone and still be hard to use at the receiving end.

For legal paperwork, the safest habit is to preserve the original layout as much as possible. See this legal faxing guide if you're sending material where signatures, page order, and legibility matter more than convenience.

Preparing a File for Submission

Start with the extension. Make sure the file is PDF, PNG, JPG, HEIC, or TIFF before you upload anything, because unsupported files need conversion first.

Then check the size and page count. If the combined submission is too large for the 20 MB cap or too long for the 100-page cap, fix that before you send. Upload errors are easier to avoid than to recover from after the file is already in motion.

A quick submission check

1. Confirm the file type. The extension should be one of the accepted formats.
2. Check total size. Make sure all attached files together stay under the fax limit.
3. Verify page order. The recipient should see pages in the same order you intended.
4. Review readability. Clean contrast and clear text matter more than file name polish.
5. Check your connection. Mobile uploads are more fragile when signal strength drops.

Filenames help too. Simple names are less likely to cause browser quirks than unusual punctuation or long chains of symbols. A stable connection matters most on a phone, where a transfer can stall if the network changes mid-upload.

A short checklist like this catches most preventable mistakes before they turn into a failed submission. It also helps when you're sending sensitive documents and want the first attempt to count.

Troubleshooting Upload Failures

Most upload failures map to one of four causes, the format, the size, the page count, or the connection. If you know which category the error belongs to, the fix gets much faster.

An unsupported format error usually means the file is something outside the accepted set, such as DOCX, DOC, BMP, GIF, or WEBP. The clean fix is to convert it to PDF, PNG, or JPG before trying again.

A file too large message points to the 20 MB total cap. Compress the PDF, reduce JPG quality slightly, or split the document into two fax jobs if the content allows it.

A page count error means the file exceeds 100 pages after rendering. In that case, divide the submission or remove pages that don't need to be faxed.

Rule of thumb: when the error names a limit, change the file. When it names the device or network, change the environment.

A blank page, upside-down page, or missing page order usually traces back to capture quality. Rotate the file, fix the scan orientation, and verify the sequence before uploading again.

Phone upload failures often come from a weak connection, a locked screen, or a file that's still syncing from iCloud or Google Photos. If the file isn't fully local yet, wait until syncing finishes and try again on a stable network.

Converting Files Before You Fax

Word files, spreadsheets, and web pages usually convert more cleanly as PDF than as screenshots. Exporting them through Print or Save as PDF keeps text sharper than a photo of the screen would.

HEIC photos from iPhone or iPad can also be converted before sending if you want broader compatibility. Use the Photos app share flow, choose a compatible output, or open the file in Preview and export it as JPG on a Mac.

If a file is too large, use built-in tools before reaching for a separate app. macOS Preview can compress TIFF and JPG files, Windows can resize images through built-in tools, and most browsers can export PDF at standard quality.

Keep the original file when you reduce size or resolution. Some conversion tools split pages or drop content during export, so it's smart to check the final page count and readability before you upload.

The safest habit is to compare the converted file against both fax limits again. A document that was fine before conversion can become too large, too long, or oddly ordered after the export step.

Quick Reference for Supported Formats

PDF is the most reliable choice when page order and layout matter. PNG is better when you need clarity and sharp edges. JPG is practical for photos, HEIC is convenient for Apple-device capture, and TIFF is useful when scan quality matters more than file size.

If you send faxes only once in a while, keep one simple rule in mind. Choose the format that preserves the document's content with the least extra work, then check the size and page limits before you upload.

If you need a straightforward way to send documents without guessing which file type will work, PerPageFax accepts the common formats covered here and keeps the rules clear up front. Visit PerPageFax to review the upload path, check your file against the limits, and send your fax with fewer surprises.