We compared the leading PST and OST viewers — CoolUtils PST Viewer, SysTools, Kernel, Stellar, Aryson and Microsoft Outlook — on the things that actually matter: opening PST and OST files without Outlook, previewing emails and attachments, offline privacy, export and price. One tool comes out on top for anyone who needs to read Outlook data files quickly and safely.
Of every tool we tested, CoolUtils PST Viewer offers the most complete free viewing experience: it opens both PST and OST files with no Microsoft Outlook installation required, shows your emails, attachments and full message headers, and keeps everything local on your own PC — no cloud uploads.
It is the best choice for anyone who needs to open, read and browse Outlook data files fast — without buying a full Outlook license or handing sensitive mail to an online service.
A side-by-side look at how the most popular PST and OST viewers stack up on the features that matter when you just need to open and read Outlook files.
| Feature | CoolUtils PST ViewerCoolUtils | SysTools PST ViewerSysTools | Kernel Outlook PST ViewerKernel | Stellar ViewerStellar | Aryson PST ViewerAryson | Microsoft OutlookMicrosoft |
|---|---|---|---|---|---|---|
| Opens PST files | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Opens orphaned OST files | ✓ | Limited | ✓ | Limited | Limited | ✗ |
| No Outlook install required | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ Is Outlook |
| Preview emails & message headers | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| View attachments | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Sort by sender / date / recipient | ✓ | ✓ | ✓ | ✓ | Partial | ✓ |
| Export / save emails (e.g. to EML) | ✓ | ✗ Paid Pro | ✗ Paid tool | Paid tier | Trial cap | ✓ |
| Reads corrupted / damaged files | ✓ | Partial | ✓ | ✓ Repair | Partial | ✗ |
| Files stay on your PC (privacy) | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Generate reports from mail data | ✓ | Partial | Partial | Partial | ✗ | Add-ins |
| Windows compatible | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Modern, easy-to-use interface | ✓ | Dated | Moderate | ✓ | Moderate | ✓ |
| Price to view files | Free (personal use) | Free viewer | Free viewer | ~$49+ paid | Free / trial | Paid license |
| Price to also export | Included | ~$49+ Pro | ~$49+ tool | ~$79+ repair | ~$49+ paid | Incl. w/ license |
✓ Full support
Partial / limited
✗ Not available
Competitor prices are approximate and vary by edition, licensing and region; free "viewers" from some vendors funnel export into a separate paid product. Verify on each vendor's site before purchase.
How CoolUtils PST Viewer compares against each major alternative — and where it pulls ahead.
SysTools PST Viewer is a popular, genuinely free viewer with a clean message preview and a large user base — plenty of people reach for it first. It's a solid choice for a quick look inside a PST.
The catch: actually saving or exporting the mail you find is pushed into a separate paid "Pro" tool, the interface feels dated, and OST support is more limited. CoolUtils PST Viewer opens both PST and OST, previews attachments and headers, and doesn't dead-end you the moment you want to keep a message.
Kernel's free viewer is legitimately good at opening corrupt or damaged PST files — if your file is broken, it's a reasonable place to start, and it handles OST too.
But like SysTools, Kernel locks export and saving behind a separate paid product, so the "free" tool is really a preview window that nudges you toward a purchase. CoolUtils PST Viewer gives you viewing of PST and OST plus everyday saving in one free tool, without the second checkout.
Stellar has one of the strongest PST repair engines on the market. If your file is seriously corrupted and you need forensic-grade recovery, Stellar is a heavyweight worth knowing about.
That power comes at a price: Stellar is expensive and built around repair, not lightweight everyday viewing. If you simply need to open a healthy PST or an orphaned OST and read your mail, it's overkill. CoolUtils PST Viewer is a fast, free, focused viewer for exactly that job.
Aryson PST Viewer does preview attachments and can open Outlook files without Outlook installed, which covers the basics for a casual look.
It's a lesser-known tool, sorting and reporting are more limited, and export is capped in the trial until you pay. CoolUtils is a well-established name (converting and viewing files since 2003) with broader viewing features, and it doesn't throttle you at an arbitrary trial limit just to read your own mail.
Microsoft Outlook is, of course, the native home of PST and OST files — nothing renders them more faithfully than Outlook itself, and if you already run it, it's right there.
But Outlook requires a paid Microsoft 365 / Office license and a full, heavy install, and it famously cannot open an orphaned OST on its own — an OST left behind by a removed mailbox is unreadable in Outlook without extra tooling. CoolUtils PST Viewer opens both PST and OST standalone, with no license and no full Outlook install.
Six reasons people pick it over every alternative in this comparison.
Read Outlook PST files and orphaned OST files — including OSTs left behind by a removed mailbox that Microsoft Outlook can't open on its own.
View and read your Outlook data files with no Microsoft Outlook installation — no heavy Office install and no paid license just to look inside a file.
See the full message — body, complete headers and attachments — and sort your mail by sender, recipient, date and time to find what you need fast.
100% offline. Your mail never leaves your computer — no cloud uploads, ideal for confidential correspondence and anyone who can't risk a data leak.
Access data from corrupted or damaged PST files that other tools choke on, and generate detailed reports from your mailbox for organization and insight.
Free for personal use with full viewing features, from a name that's converted and viewed files since 2003 — not a trial window that upsells the basics.
Weighted across PST & OST support, preview quality, privacy, export, ease of use and price.
Quick answers to the questions people ask most when choosing a PST viewer.
For opening and reading PST and OST files without Microsoft Outlook, CoolUtils PST Viewer is our top pick. It opens both PST and orphaned OST files, previews emails, headers and attachments, keeps everything local on your own computer, and is free for personal use — where rivals like SysTools and Kernel push export into a separate paid product.
Yes. CoolUtils PST Viewer reads Outlook data files directly, with no Microsoft Outlook installation and no Office license required. You avoid both the cost of an Outlook license and the disk footprint of a full Office install just to look inside a PST.
Yes — and this is a key advantage. Microsoft Outlook cannot open an orphaned OST (one left behind after its mailbox is removed) on its own. CoolUtils PST Viewer opens both PST and OST files standalone, so you can read mail from an OST even when the original account is gone.
With CoolUtils PST Viewer, yes — it works entirely offline, so your mailbox never leaves your machine. Unlike online converters that upload your data to a third-party server, a local desktop viewer keeps confidential correspondence private on your own PC.
It depends on the tool. Several popular "free" viewers (such as SysTools and Kernel) let you preview messages for free but require a separate paid product to actually export or save them. CoolUtils PST Viewer is free for personal use with full viewing features, so you're not stopped the moment you want to keep a message.
See why CoolUtils PST Viewer beats the alternatives. Download it and start reading your Outlook files immediately — no registration required.
✓ Open both PST and OST files
✓ No Microsoft Outlook install required
✓ Preview emails, headers and attachments
✓ Everything stays local — no cloud uploads
✓ Free for personal use
Windows Compatible • 38MB Download • Instant Setup