How to Send a Fax Online
You need to send a fax, but you don't have a fax machine. Maybe you are filing your taxes with the IRS, sending a signed contract to a law firm, or submitting documents to an insurance company. Whatever the reason, you are not alone. Millions of people every year find themselves in exactly the same situation.
The good news: you can send a fax online from any device with a browser. No fax machine, no phone line, no apps to install. This guide walks you through exactly how it works, how to prepare your documents, and what to watch out for.
What is online faxing?
Online faxing lets you send a document to a traditional fax machine using a web service instead of physical hardware. You upload a file -- typically a PDF -- enter the recipient's phone number, and the service converts your document into a fax signal and transmits it over the phone network. The receiving fax machine prints out the document just as if you had sent it from a fax machine yourself.
From the recipient's perspective, there is no difference. They receive a normal fax. The only thing that changes is how you send it.
What you need before you start
Before you open any fax service, make sure you have these three things ready:
The recipient's fax number. This is the most important detail, and the most common source of errors. Double-check the number, including the country code, as most services support international faxing. If you are faxing a government agency or large organization, their fax number is usually listed on their website or the form itself.
Your document in a supported format. Most online fax services accept PDF, and many also support image formats like PNG, JPEG, and TIFF. PDF is the most reliable choice as it preserves formatting, keeps pages in order, and produces the best print quality on the receiving end. If your document is in Word or another format, we suggest you convert it to a PDF first.
A payment method. Pay-per-use services typically accept major credit cards, and some also support PayPal, Apple Pay, Google Pay, and other local wallet payment services. Subscription services will require a payment method upfront, usually even during a free trial, and will be charging you monthly.
How to prepare your document
Fax is basically a print technology. The receiving machine prints your document on paper, usually in black and white. This means document quality matters more than you might expect.
Use black text on white background. Fax machines render everything in monochrome, so colored text or low-contrast designs may come out faint or unreadable. If your document has colored elements, check how it looks when printed in grayscale.
Make sure text is legible at print size. Small fonts -- anything below 10pt -- can become hard to read after fax compression. If you are including fine print or footnotes, consider bumping the size up slightly.
Check that signatures are clearly visible. If you've signed a document digitally or scanned a signed page, make sure the signature has enough contrast to survive the fax process. A light pencil signature on a slightly gray background can disappear entirely.
Combine everything into a single file. If you have multiple documents to send, merge them into one PDF before uploading. This keeps pages in the right order and avoids confusion at the receiving end. On a Mac, you can do this in Preview; on Windows, most PDF readers have a merge or combine option; and free online tools work on any device.
If you are faxing contracts, court filings, or other legal paperwork, document preparation matters even more -- scan quality, signature visibility, and cover sheets can make the difference between a successful filing and a rejected one. See our guide to faxing legal documents online for the full checklist.
Step-by-step: Sending a fax online
The exact steps vary slightly between services, but the core process is the same everywhere. Here's how it works with a pay-per-use service like JustFax Online:
Step 1 — Upload your document. Go to the fax service's website and upload your file. JustFax Online supports pdf, png, jpeg, and tiff formats, with a maximum file size of 20MB and up to 200 pages per file. You'll see a confirmation of the file name, format, and page count before moving on.
Step 2 — Enter the recipient's fax number. Type in the full fax number, including the country code for international faxes. The service will show you the price before you commit. At JustFax Online, you get a flat price for the first four pages, with additional pages priced separately -- no hidden fees.
Sending to a number outside the United States? International fax numbers require a country code and often trip people up with leading-zero rules. Our guide to sending an international fax online covers number formatting, common mistakes, and tips for getting it delivered on the first try.
Step 3 — Pay and send. You'll be redirected to a secure payment page. After payment, the fax is transmitted immediately. Most small faxes (1–3 pages) are delivered within five minutes, though larger documents or busy recipient lines can take up to an hour. You'll receive an email confirmation once delivery is complete.
That's it. Three steps, no account required, done in under two minutes.
What happens after you send your fax
Once your fax is submitted, the service queues it for transmission. Here's what to expect:
You'll get a delivery confirmation by email when the receiving fax machine successfully prints your document. If delivery fails -- because the recipient's line is busy, the machine is off, or the number is wrong -- the service will retry automatically. JustFax Online retries multiple times before marking a fax as failed. If all attempts fail, the payment authorization is released, and you're not charged.
If you need to check on your fax later, JustFax Online gives you a fax ID that you can use to retrieve the status at any time.
After successful delivery, your uploaded document is deleted from JustFax Online's servers. There is no ongoing storage of your files.
Choosing the right service
Not every online fax service works the same way. The right choice depends on how often you fax and what you need.
Pay-per-use services are the best fit if you send faxes occasionally -- a few times a year, or even just once. You pay a flat fee per fax, with no account, no subscription, and no commitment. JustFax Online and similar services fall into this category. The advantage is simplicity: you see the price upfront, pay once, and you're done.
Subscription services like eFax, Fax.Plus, or Dropbox Fax make more sense if you send or receive faxes regularly -- say, weekly or daily. Monthly plans typically range from $10–30 and include features like dedicated fax numbers, cloud storage, and integrations with tools like Google Drive. The trade-off is that you're paying monthly whether you fax or not.
Free fax services exist, but come with significant limitations. Page limits are usually very low, many require account creation despite advertising as "free," and some attach ads or watermarks to your fax -- which looks unprofessional and can obscure content. For anything important, a paid service is worth the small cost.
Here are a few things to consider when deciding:
- Do you need to receive faxes, or just send? Most pay-per-use services are send-only. If you need a fax number to receive documents, you'll likely need a subscription plan.
- Are you sending domestically or internationally? Check that the service supports the country you're faxing to. JustFax Online covers 150+ countries.
- How sensitive is your document? Look for services that use SSL encryption in transit, delete files after delivery, and don't require you to create an account that stores personal data unnecessarily.
Sending a fax from your phone
You don't need a computer to send a fax online. Any smartphone or tablet with a browser works -- the process is identical. Go to the fax service's website, upload your document, enter the number, and pay.
If your document is a physical piece of paper, you can use your phone's camera or a scanning app (like the built-in scanner in iOS Notes or Google Drive on Android) to capture it as a PDF. Make sure you scan in good lighting with the page laid flat to get a clean result.
There's no need to download a dedicated fax app. Browser-based services like JustFax Online are designed to work on mobile without an app, which means one less account to create and one less app taking up space on your phone.
Looking to send a fax straight from your smartphone? You don't need an app -- your phone's browser is all it takes. Check out our step-by-step guide on how to fax from your phone, including tips for scanning documents with the built-in tools on iOS and Android.
Common mistakes to avoid
Wrong fax number. This is the single most common reason faxes fail. Always double-check the number, especially for international faxes where country codes and area codes can be confusing. If you're unsure, call the recipient to confirm their fax number before sending.
Sending a Word document instead of a PDF. While some services accept .doc or .docx files, the formatting can shift during conversion. Always convert to PDF first to ensure your document looks exactly the way you intended.
Poor scan quality. If you're scanning a physical document, make sure it's well-lit, flat, and in focus. A dark or blurry scan might be readable on your screen but illegible once it comes out of a fax machine.
Assuming "free" means no catch. Free fax services often add cover pages with advertising, limit you to a handful of pages, or require you to create an account with your personal information. Read the fine print before uploading sensitive documents to any free service.
Sending at the wrong time. Some fax machines are turned off outside business hours. If your fax fails, try resending during the recipient's normal business hours. This is especially relevant for international faxes across time zones. JustFax Online has an intelligent sending mechanism that will retry the fax for you if it detects that the machine might be off, or the fax is sent outside business hours.
Why faxing still matters
It might seem odd that faxing is still a thing in 2026, but certain industries rely on it heavily. Healthcare providers use fax for HIPAA-compliant document transfer. Government agencies -- including the IRS and Social Security Administration -- still accept and even prefer fax for form submissions. Law firms, insurance companies, and financial institutions use fax because signed faxed documents carry legal weight in many jurisdictions.
The reason is mostly regulatory and procedural inertia: fax provides a paper trail, a confirmation of delivery, and a level of point-to-point security that email doesn't inherently offer. As long as these institutions require fax, people will need a way to send them -- and online fax services make that possible without keeping a fax machine in your home.
Is it safe to send a fax online?
Yes. Online fax uses HTTPS encryption for the upload and transmits over the telephone network -- the same as a traditional fax machine. For a detailed breakdown of how each stage works, how online fax compares to email, and what to look for in a secure service, see our guide to online fax security.
Send your fax now
If you just need to send a fax and get on with your day, JustFax Online is the fastest way to do it. Upload your document, enter the number, pay once -- and your fax is on its way. No account, no subscription, no app. It works on any device and supports 150+ countries.