20 online tools that replace installed software — and the one setting to know for each

A HEIC photo sent from an iPhone that the accounts team cannot open. A 38 MB PDF rejected by a form that caps uploads at 10. A 450 MB MP4 for half an hour of a recorded meeting. These hold-ups have one thing in common: five minutes if you know the right utility, half a day if you start by hunting for software to install.

Here are twenty online tools that cover almost every one of those situations, each with the setting or the limit worth knowing before you click.

The real dividing line: where does your file get processed?

Before comparing features at all, one question splits online tools into two families.

In the first, everything happens in your browser: the file is loaded into memory, worked on through the Canvas API or through code compiled to WebAssembly, and the result is handed back to you locally. Not a single byte is transmitted. What that means in practice: a contract covered by an NDA never leaves your machine, and the tool still works behind a corporate proxy that blocks file uploads.

In the second, the file goes off to a server, because no browser can do the job on its own: re-encoding a video, rebuilding the structure of a Word document from a PDF, running a background-removal model. The question then becomes: how long is the file kept? On Convertu, one hour, then deletion. A service that will not answer that clearly does not deserve your file. Of the sixty tools in the catalogue, forty-one run browser-side; the other nineteen go through the server.

PDF: the five jobs that keep coming back

1. Merging several PDFs. The classic case is a bundle of paperwork: proof of address, bank statement and photo ID in a single upload. Two things to watch. The order is the order of the list, not the order of your filenames, and the sizes add up — three 9 MB files give a 27 MB PDF, which needs compressing before it goes anywhere.
2. Splitting a PDF. Pulling pages 12 to 18 out of a 200-page report saves sending 40 MB to someone who will read seven of them. It is also the simplest way of leaving a confidential annex out.
3. Compressing a PDF. The only real lever is the resolution of the embedded images. Going from 300 DPI (print quality) down to 150 DPI (plenty for reading on screen) often cuts the size by a factor of three or four. The corollary: a PDF made up almost entirely of text will gain nothing, because that is not where its size comes from. If your 30 MB file is a scan, compressing the PDF settles it; if it is 30 MB for ten pages of text, start looking for an unusual font embedded in full.
4. PDF to Word. The conversion works provided the PDF contains a genuine text layer. Two-second test: try selecting a word with the mouse. If nothing highlights, you have a scan — one image per page — and no conversion will hand you editable text without optical character recognition (OCR). Expect to tidy the layout too: columns and merged table cells are rarely rebuilt exactly as they were.
5. JPG to PDF. For sending photographs of documents to a council or government portal that accepts nothing but PDF. Check the orientation: a photo flagged as rotated in its metadata can end up lying on its side in the finished document.

Images and video: taking back control of file size

6. Compressing an image. JPEG quality 80 is the classic sweet spot: below 60, flat areas and gradients start showing the algorithm's 8 × 8 pixel blocks. Rough figures: a 4000 × 3000 photo weighs 6 to 8 MB; brought down to 1600 px wide at quality 80, it falls under 300 KB with no difference you can see on screen. Image compression runs entirely in your browser, and the tool page states the largest file it will take.
7. Resizing an image. The gain comes from the dimensions first, not from the compression ratio: an image for web content rarely needs to be more than 1920 px wide, a thumbnail 400 px. Going from 4000 to 1600 px divides the pixel count by more than six.
8. HEIC to JPG. Since iOS 11, iPhones have saved in this format by default. A HEIC file is about half the size of a JPEG at the same quality, and unreadable for plenty of business software and older Windows machines. The HEIC to JPG converter bridges the gap. On the iPhone itself, the "Most Compatible" option under Settings → Camera → Formats removes the problem at source.
9. Removing the background. Absolute rule: save the result as PNG. Turn it back into JPEG and the cut-out disappears, the background going white or black again. The limits are always the same: fine hair, glass, wire mesh, objects the same colour as the background.
10. MP4 to MP3. For listening to a talk again on the move without carrying a video file around. For speech, 128 kbps is more than enough; keep 192 to 256 kbps for music.
11. Compressing a video. A 1080p screen recording of a meeting stays perfectly readable at 720p, for roughly half the size. Check the maximum size shown on the tool page before you send up a long recording.

Text, web and development: the everyday kit

12. JSON formatter. It indents, but above all it validates: the quickest way to find the stray comma that makes an API import fail.
13. Base64 encoder and decoder. For reading a fragment you have come across in a log, or an image embedded as a data URI. Worth keeping in mind: this is not encryption, only a representation.
14. URL encoder. It explains why a link breaks the moment it contains a space, an ampersand or an accented character, and it lets you rebuild clean campaign parameters.
15. Password generator. The key point: this password generator runs in the browser, and the string it produces is never sent anywhere. Sixteen random characters for a critical account, a four-word passphrase when you have to remember it.
16. QR code generator. One detail that changes everything in print: the longer the address, the denser the matrix and the harder it is to scan at small sizes or from a distance. Shorten the URL before you generate, not after.
17. The trio of thankless jobs: word counter, duplicate remover, case converter. Cleaning up a list of addresses pasted out of a spreadsheet, sticking to a word count, putting a badly typed export back into lower case.

A slug generator, a Markdown to HTML converter and MD5 and SHA hashes round out the kit as soon as a website is involved.

Calculations: the ones you will reopen most often

18. VAT calculator. Going from an ex-VAT figure to an inc-VAT one or back again, at the right rate, without getting the direction wrong halfway through writing a quote.
19. Currency converter. For pricing an invoice or an expense claim in the client's own currency.
20. Time zone converter. Setting up a video call across London, New York and Singapore without dragging anyone out of bed at three in the morning.

The gap between two dates, percentage calculations and unit conversion play the same role. They all run locally in the browser, with nothing to upload.

The traps that make a conversion fail

Four causes explain most disappointing results.

• The scanned document. It looks like a PDF, but it is an image. No conversion to Word, no text search and no copy-and-paste will work until OCR has been run on it.
• Lost transparency. JPEG has no way of storing transparent areas. A logo cut out and then saved again as JPEG comes back with an opaque background. PNG for transparency, JPEG for photographs.
• Fonts that are not embedded. A PDF generated without embedding its fonts displays correctly on the machine that made it, then shifts everywhere else, the reader substituting something approximate. It shows up mainly in tables and headings, and the fix belongs at the export stage.
• EXIF metadata. A smartphone photo carries the date, the camera model and, very often, the GPS coordinates of the spot where it was taken. A resize carried out in the browser, through the Canvas API, strips them on the way through — but that is not automatic: plenty of editing tools copy them across untouched, GPS coordinates included. Check the output file before you publish.

Then there is size. Browser-side processing works inside the memory of the tab, entirely comfortable with images and text, far less so with several gigabytes of video. That is where the server takes over.

The right habit fits into one sentence: pick the tool according to where the file will be processed, then check the one setting that matters for the job in hand. Thirty-six of the forty-one tools that run in the browser are used with no account and no daily limit; the five image tools, local as well, ask for an account and belong to the subscription. Where a maximum file size applies, the tool page says so. On the nineteen server tools, one conversion a day is free without signing up, and unlimited use goes through a single subscription at €7 a year, cancellable in one click. The full catalogue stays free to browse.