Online File Tools And Whether Yours Uploads

Online file tools come in two designs that share one name. Online tool means two entirely different things and the difference is whether your file leaves your machine. One kind sends it to a server and works on it there. The other sends you the code and works on the file where it already sits. Both are described with the same words. Telling them apart takes about thirty seconds.

That matters more with mail than almost anything else. A mailbox is not one document. It is every document, every address and every conversation somebody has had, in one file. Deciding where that file goes is worth more than a moment's thought.

Two Online Tool Designs Wearing One Name

Both sit at a web address. Both ask you to choose a file. What happens next is where they part.

choose file
  file uploads
  server does the work
  result downloads

your file was on
  somebody else's disk

page loads
  code arrives
  browser does the work
  result saves locally

your file never
  left the machine

The padlock settles none of this. It means the connection is encrypted while data moves. It says nothing about whether your data moved at all. It says nothing about what happens after it arrives. Three separate questions, one answer.

How the Browser Became Able to Do This

Local processing was not practical for a long time, which is why uploading became the norm. Two things changed that.

The File API gave pages a way to read a file you choose without sending it anywhere. WebAssembly then let real programs run in a tab at close to native speed, so parsers written in other languages could work inside a browser rather than on a server.

Plenty of tools still upload because they were built before this was possible. The design is not always a decision about your data. Sometimes it is just the year the tool was written, which is worth remembering before assuming anything about intent.

Checking an Online Tool Yourself in Half a Minute

You do not have to take anybody's word for this, including ours. The browser will tell you.

1. Open the network panel before choosing a file. Right click, Inspect, then Network. Leave it open.
2. Choose your file and watch the list. An upload appears as a single request carrying roughly the size of your file. A ten megabyte file makes a ten megabyte request. It is hard to miss.
3. Read the size column rather than the names. You are looking for one large outgoing entry. Small requests are the page fetching its own pieces.
4. Then try it with the network off. Load the page, disconnect, use the tool. Anything that keeps working is doing the work locally, because there is nowhere else left for it to happen.

Disconnecting settles what a policy cannot. A privacy policy is a promise. A tool that finishes the job with the network switched off is a demonstration. It takes less time to run than reading the policy would.

What Each Online Tool Design Actually Costs

Local processing is not free of trade-offs. Any page claiming otherwise is selling something.

The middle rows are the honest cost. A browser tab has far less memory than an installed program, so a very large file can fail in one and open in the other. That limit is real and it moves as machines improve.

Why Mail Files Raise the Stakes

Most file tools handle one document at a time. Mail files do not work that way.

A PST from a working mailbox holds years of correspondence, every attachment anybody sent, the addresses of everyone involved and a good deal about who spoke to whom. Uploading one is a different act from uploading a photograph, even where the tool is entirely trustworthy.

The last row is the one that catches organisations. Uploading a colleague's mailbox to a service you have not assessed makes a decision on behalf of everybody who wrote to them. Under data protection rules that is a processor relationship. It needed thinking about before the file was chosen rather than after.

When Uploading Your File Is the Right Answer

None of this makes uploading wrong. It makes it a decision rather than a default.

Local processing is not an argument for never uploading. It is an argument for knowing which one you picked, since at the moment most people cannot tell and the page rarely says.

What This Site Does And How to Check It

Our viewers and converters read files in the browser. Nothing is uploaded and no copy exists on our side, because there is nowhere for one to be.

That is a claim like anybody else's, so do not take it on trust. Open the network panel and load a mailbox. Then disconnect and do it again. The second test is the one that means something. It applies just as well to every other tool you use.