Someone emailed me an HTML file: how do I open it from Outlook?

A client emails you page.html, a page an AI built for them. A teacher sends a quiz as quiz.html. You open the email in Outlook, click the attachment, and want the page they saw, with its buttons working. Microsoft's help doesn't say what Outlook's preview shows for an .html file, and a page's scripts need a browser to run. This guide covers how to get the file out of Outlook on Windows, on a Mac, on the web, on an iPhone, and on Android, how to open it so it works, and what Outlook's warnings mean. If you're the one sending, How to send an HTML file by email covers your side.

The Microsoft, Apple, and Google help pages quoted here were read on November 6, 2026. We didn't test any Outlook app or Outlook on the web. The device results below come from our earlier tests of the file itself, on an Android emulator, an iPhone simulator, and a Mac. We haven't tested a Windows PC.

The quickest way on any phone or computer: save the attachment to your device as in step 2, open Convika's free HTML viewer in your browser, click or tap Choose an .html file, and pick the file. Your browser reads the file, and it isn't uploaded. If someone sent you a file you weren't expecting, ask them first, and turn off Run scripts before you choose it.

What Outlook does with an .html attachment

Microsoft's help covers opening, previewing, and saving attachments in each Outlook app, and lists the file types Outlook blocks. .html and .htm aren't on that list. Microsoft doesn't say what you see when you click or tap an .html attachment, in any Outlook app. It says the previews in new Outlook, classic Outlook, and Outlook for Mac open files from "most Microsoft Office/Microsoft 365 programs including Word, PowerPoint, Excel, and Visio", and "attached Outlook email items, images, and text files". It doesn't say whether an .html file counts as a text file there.

The steps for iOS and Android come from Microsoft's guide for people who use a screen reader. It's the only Microsoft help we found on saving a received attachment in the Outlook phone apps. It names Save to device on Android, but not the button you tap next to the attachment to get there.

The "can only be saved" line comes from Microsoft's reference for the admins of work and school mailboxes, on Exchange and Microsoft 365. Its list of the files Outlook on the web lets you save but not open includes .htm and .html by default. An admin can change the list. Microsoft doesn't say whether it applies to a personal Outlook.com account or to new Outlook for Windows.

Open an HTML attachment from Outlook in 4 steps

These steps get the file onto your device and open it in a browser, where its scripts run. Nothing is uploaded.

1. Check who sent it

Look at the sender before you open the attachment. Microsoft's own advice is to "be careful in opening any attachment, especially if it's from someone that you don't know or trust. When in doubt, confirm the authenticity of the attachment with the sender." Ask by phone or in a new message, not by replying. Is it safe to open an HTML file? lists the red flags.

2. Save the attachment

• New Outlook for Windows: select the arrow next to the attachment, select Download, choose a folder, and select Save. You can also drag the attachment from the message to your desktop.
• Classic Outlook for Windows: select the arrow to the right of the attachment, choose Save As, and save it. Microsoft says attachments go to your Documents folder by default.
• Outlook for Mac: select the arrow next to the file, select Download, and choose a place to save it in Finder.
• Outlook on the web or Outlook.com: open the message, select More actions next to the attachment, select Download, and choose where to save it.
• iPhone: in Outlook, tap the attachment. Outlook loads a preview. Tap Share, then Share file via…, then Save to Files. Choose a folder on your iPhone and tap Save. Microsoft says you then find the file in the Files app.
• Android: in Outlook, open the email and choose Save to device for the attachment. Microsoft's steps, written for the TalkBack screen reader, reach it from the control right after the attachment, and don't name that control. If Android asks to let Outlook reach your files, tap Allow. Microsoft says you then find the file "in the Downloads folder in the Files app."

3. Open it in a browser

• Windows: double-click the file, and Windows opens it with the app set for .html files. If that app shows code, open Microsoft Edge or Google Chrome, press Ctrl + O, and choose the file. Microsoft lists that shortcut in Edge as "Open a file from your computer in Edge". To have every .html file open in a browser, open Settings > Apps > Default apps, type .html, select the result, and choose a browser, as Microsoft's steps give it. How to open an HTML file on Windows covers the rest.
• Mac: double-click the file in Finder, and it opens in the app your Mac uses for .html files. If that app shows code, open Chrome or Edge, press ⌘ + O, and choose the file. In our macOS 26.5.2 test, Chrome ran the scripts of a file opened from disk. How to open an HTML file on a Mac shows how to make a browser the app for every .html file.
• Android: open Files, go to Downloads, tap the file, choose Chrome, then Just once. In our Android 16 emulator test, Chrome ran the page's scripts and Android's HTML Viewer didn't. On a Samsung Galaxy, the file app is My Files: see how to open an HTML file on a Samsung phone.
• iPhone: Apple's Files guide says: "If you haven't installed the app that created a file, a preview of the file opens in Quick Look." That preview ran no JavaScript in our iOS 26.3 test, so a quiz or a game won't respond there. Use step 4 instead.

4. Or open it in the HTML viewer

Open Convika's free HTML viewer in your browser and click or tap Choose an .html file. On Android, if the file picker opens on Recent, open the menu at the top left and choose Downloads. On an iPhone, pick the file from the folder you saved it in. The page runs inside the viewer with its scripts, and the file isn't uploaded. The viewer opens .html and .htm files up to 2 MB. If someone sent you a file you weren't expecting, ask them first, and turn off Run scripts before you choose it.

Why the attachment won't open or download

• Outlook on the web lets you download it but not open it. On a work or school account, that's the default for .htm and .html files, as above. Download it and open it from your downloads, as in step 3.
• Outlook says it "blocked access to the following potentially unsafe attachments". Microsoft's help for Outlook 2010 to 2016 says that when Outlook blocks an attachment, "you can't save, delete, open, print, or otherwise work with the attachment in Outlook." .html isn't on Outlook's list, so the file is another type, such as .mht or .hta, or your organization blocks more types than the list. Microsoft's advice for a blocked file: "ask the sender to upload the file to OneDrive or SharePoint and send you a link."
• Outlook on the web says "Access to attachments has been blocked." Microsoft gives that error for Microsoft 365 accounts, when Outlook on the web blocks the file's type. .htm and .html aren't on its default list either, so ask your IT team, or ask the sender for a link.
• The preview shows nothing, or only code. Microsoft doesn't say what the preview shows for an .html file, and in classic Outlook it disables scripts in a preview. Save the file and open it in a browser.
• It opened, but shows code or doesn't respond. The app that opened it isn't a browser, or runs no scripts. Open it in a browser, as in step 3. If pictures and styles are missing, the page needs files that were saved next to it, and only the .html file came with the email. Why does my HTML file open as code (or a blank page)? goes through each cause.

Ways to open it, compared

Is an HTML attachment in Outlook safe to open?

Outlook doesn't block .html files by type. Its list of blocked file types has .hta, .htc, .mht, .mhtml, and .js, but not .htm or .html. A phishing page needs no blocked file type: Microsoft's researchers have documented HTML attachments that show a fake sign-in box and send the password to the attacker, as Is it safe to open an HTML file? explains.

So open one only if you expected it and know who sent it. To look at a file you weren't expecting without running it, open the HTML viewer and turn off Run scripts before you choose the file: the page then shows its HTML and CSS only. Don't type a password into a page that came as an attachment.

At school or work, report a file you didn't expect to your IT team instead of opening it.

Ask the sender for a link

A link skips every step above. Microsoft gives the same advice for a file Outlook blocks: ask the sender to upload it and send you a link. The sender puts the page at a web address and pastes that address into the email. You click it in Outlook, and the page opens in your browser with its buttons working, if the host runs its scripts. Convika is one such host: the sender uploads the file, publishes it, and sends an address like yourpage.convika.page.

If you're the sender, How to send an HTML file by email covers attaching the file in Gmail, Outlook, and iPhone Mail, and the 4 steps to send it as a link instead. How to share an HTML file as a link compares other free hosts.

Frequently asked questions

How do I open an HTML attachment in Outlook?

Save it, then open it in a browser. In new Outlook, Outlook for Mac, and Outlook on the web, choose Download in the menu next to the attachment; in classic Outlook, choose Save As. Then double-click the file, or open Edge or Chrome, press Ctrl + O (⌘ + O on a Mac), and choose it. Convika's free HTML viewer opens it in any browser without uploading it. If you weren't expecting the file, ask the sender first, and turn off Run scripts before you choose it.

Can Outlook preview HTML files?

Microsoft doesn't say. Its help says Outlook's preview opens files from Word, PowerPoint, Excel, and Visio, and email items, images, and text files, and doesn't say whether an .html file is one of them. In classic Outlook, scripts are "disabled during a preview", so a quiz or a game won't work there. To see the page working, save the file and open it in a browser.

Does Outlook block HTML attachments?

No. Microsoft's list of file types blocked in Outlook has .hta, .htc, .mht, and .mhtml, but not .htm or .html. On a work or school account, Outlook on the web lets you save an .htm or .html attachment but not open it, by default. An admin can change what a work or school mailbox blocks.

Why does Outlook only let me download an HTML attachment?

On a work or school account, Outlook on the web treats .htm and .html as files that "can only be saved" from Outlook on the web, "not opened", unless an admin changed that. Microsoft's admin reference lists both among the defaults. Download the file and open it in your browser.

How do I open an HTML attachment from Outlook on my iPhone?

In Outlook, tap the attachment, tap Share, Share file via…, and Save to Files, and save it to a folder on your iPhone. Tapping the file in Files opens Quick Look, which ran no JavaScript in our iOS 26.3 test. In Safari, open Convika's HTML viewer and choose the file: its scripts run there. If you weren't expecting the file, turn off Run scripts first.

Where do Outlook attachments download on Android?

Microsoft says an attachment you save with Save to device goes to "the Downloads folder in the Files app." Android's help says "you can usually find your files in the Files app," and that if you can't find that app, "your device manufacturer might have a different app." On a Samsung Galaxy, the app is My Files.

Is it safe to open an HTML attachment in Outlook?

Yes, if you expected it and know who sent it. Outlook doesn't block .html files, and an HTML file can show a fake sign-in box. If you weren't expecting it, ask the sender in a new message. Then open it in the HTML viewer with Run scripts off before you open it in your browser. Don't type a password into it.

Sources

• Open, save, and edit attachments received in Outlook (Microsoft Support) (checked November 6, 2026)
• Blocked attachments in Outlook (Microsoft Support) (checked November 6, 2026)
• Troubleshoot attachment problems in Outlook for Windows (Microsoft Support) (checked November 6, 2026)
• View and save attachments in Outlook for Mac (Microsoft Support) (checked November 6, 2026)
• Preview attachments in Outlook for Mac (Microsoft Support) (checked November 6, 2026)
• Use a screen reader to save an image or attachment from an email in Outlook (Microsoft Support) (checked November 6, 2026)
• Outlook blocked access to the following potentially unsafe attachments (Microsoft Support) (checked November 6, 2026)
• Can't open or view attachments in Outlook on the web (Microsoft Learn) (checked November 6, 2026)
• Set-OwaMailboxPolicy (Microsoft Learn) (checked November 6, 2026)
• Keyboard shortcuts in Microsoft Edge (Microsoft Support) (checked November 6, 2026)
• Change default apps in Windows (Microsoft Support) (checked November 6, 2026)
• Chrome keyboard shortcuts (Google Chrome Help) (checked November 6, 2026)
• Find and view files and folders in Files on iPhone (Apple) (checked November 6, 2026)
• Find & delete files on Android (Android Help) (checked November 6, 2026)