Disclosure: I made Pdfle, one of the tools mentioned below. I've tried to list it alongside the other options and be upfront about its limits.

Sooner or later someone sends you a file your machine can't open. A .vsdx diagram, a .heic photo from an iPhone, a .pptx when you don't have Office, or a spreadsheet on a borrowed laptop. Installing a full office suite to look at one file is overkill, so here's a rundown of browser-based options, organised by file type, with the trade-offs of each.

Office documents: DOCX, XLSX, PPTX

Microsoft 365 on the web. With a free Microsoft account you can open and edit Word, Excel and PowerPoint files at microsoft365.com. Files get saved to OneDrive (the free tier comes with 5 GB). This is the most faithful option for complex documents, since it's Microsoft's own renderer. The catch is that you need to sign in and keep the file in OneDrive.

Google Drive / Docs, Sheets, Slides. Drive can preview .doc/.docx, .xls/.xlsx and .ppt/.pptx files, and you can open them in Docs, Sheets or Slides for editing. Fine for most everyday files. Heavily formatted documents, macros and some fonts may not come through exactly. Also requires a Google account.

No-account viewers. If you just want to look at a file quickly, without signing in to anything, there are browser tools that open the file directly. Pdfle (mine) is one of these: it has viewers for DOCX, XLSX and PPTX and converters between formats. The viewers handle files up to 25MB. It's simpler than a full office suite, so for complex layouts the Microsoft or Google options above will be more accurate.

Visio diagrams: VSDX

This one trips people up because Visio is a separate paid product.

  • draw.io (app.diagrams.net) can import .vsdx files (File > Import, or drag the file onto the canvas) and lets you edit them. It also handles the older binary .vsd format. It can't import the 2003–2010 XML formats (.vdx, .vsx); those need to be re-saved as .vsdx in Visio first.
  • Microsoft's free Visio viewer lets you view Visio files stored in OneDrive in a browser, after signing in with a Microsoft account. Editing in Visio for the web is only included in certain business Microsoft 365 plans.
  • Pdfle also has a VSDX viewer, if you only need to look at the diagram without an account.

If you need to edit the diagram, draw.io is the best free choice here.

iPhone photos: HEIC / HEIF

HEIC is Apple's default photo format, and it's still awkward elsewhere.

  • Safari 17 and later (macOS and iOS 17+) can display HEIC images natively. Chrome and Firefox can't, so on Windows or Linux you'll usually need to convert.
  • Google Photos accepts .heic uploads, but note that Google Drive doesn't list HEIC among the image types it previews.
  • Online converters turn HEIC into JPG or PNG. CloudConvert is a well-known general-purpose one; its free plan gives you 10 conversion credits per day (some conversion types use more than one credit). Pdfle has a HEIC/HEIF-to-JPG/PNG converter too.

Tip: if you control the iPhone, Settings > Camera > Formats > Most Compatible makes it shoot JPEG instead, which avoids the problem going forward.

PDFs

Every modern browser has a built-in PDF viewer, so for reading a PDF you don't need anything extra. For merging, splitting, compressing or converting PDFs to Word/Excel, you'll want a dedicated tool. Pdfle's PDF tools (merge, split, compress, PDF to Word/Excel/PowerPoint, Word/Excel to PDF) are free with no sign-up, but currently limited to 2MB files. That's fine for typical forms and short documents, but too small for large scanned files. For big PDFs, a desktop tool or an account-based service is the more practical route.

A note on uploading files

Many online converters process your file on their servers. That's normal and often necessary, but for sensitive documents (contracts, IDs, medical records) it's worth checking each service's privacy policy, or using a desktop app instead. This applies to every tool in this list, mine included.

Quick reference

File Quick view, no account Best for editing Notes
DOCX / XLSX / PPTX No-account viewer (e.g. Pdfle) Microsoft 365 web (free account) Google Docs/Sheets/Slides also work
VSDX Pdfle viewer, MS Visio viewer (sign-in) draw.io .vdx/.vsx not supported by draw.io
HEIC Safari 17+ n/a, convert to JPG CloudConvert free tier: 10 credits/day
PDF Built-in browser viewer Depends on task Pdfle PDF tools: 2MB limit

Wrapping up

There's no single tool that's best for everything. For faithful editing of Office files, Microsoft's own web apps are hard to beat. For Visio, draw.io is the go-to free option. For a quick look at a file without signing up for anything, a no-account viewer saves time.

If you try Pdfle, I'd appreciate feedback, especially files that don't render correctly or formats you'd like added. And if there's a browser tool for awkward formats that I missed, drop it in the comments.