How to search your Proton Mail messages

Reading: 8 mins
Category: Search and organize emails

Proton Mail uses zero-access encryp tion to store all emails at rest, and emails sent between Proton Mail users are fully end-to-end encrypted. So we can’t read the contents of your emails.

To preserve this level of privacy, we’ve created a search function that allows you to search your emails without giving our servers access to your messages.

Learn how to search your messages privately to find that one email you’re looking for.

Searching email content with the web and desktop apps
Searching email content on iOS, iPadOS, and Android
Content search privacy and security
Searching email content with Proton Mail Bridge
Advanced search
- How to use it
- How to search using advanced syntax

Searching email content with the web and desktop apps

You can search the contents of your encrypted emails without giving Proton Mail access to those messages. We achieve this in the web app and the Proton Mail desktop app by creating a local index of your emails and storing it using your browser’s web storage(new window).

When you perform a content search in the web or desktop apps, Proton Mail goes through the index of your downloaded emails and highlights all matches, so your emails do not need to be searched on our servers. Your emails remain private and secure, as the emails are searched locally on your device.

Content search is off by default, so to use the feature, you must turn it on.

How to enable search message content

In the Proton Mail web app, click in the Search messages box at the top.

Click Enable.

Click Enable to confirm. Your messages will then be downloaded from Proton Mail’s servers, decrypted, and indexed locally in an encrypted state.

This process may take a few minutes and can be quite resource-intensive.

Click Pause if you want to pause indexing and resume later. You can still perform a standard search (not including message content) while indexing is in progress by clicking Search. To further refine your search, click More search options.

Note: If you’ve indexed your message content before but used a different browser or device, you’ll need to create a new index by following these steps again.

Once the indexing is complete, you can search for one or more keywords in the search bar, which will return results that include the contents of your messages.

Note:

Your index will be updated automatically — new emails will be added regularly as long as Proton Mail is open in your browser or the desktop app.
If you haven’t used your browser for some time, the index might need a few seconds to update before you can search message content again.
If your mailbox is very large and you don’t need to search message content, you can speed up searches by disabling search message content. The index won’t be erased if you do this.

In rare cases, the contents of a large inbox may require more storage capacity than your browser offers.

If so, a date will be displayed showing how far back in time you can search the contents of your encrypted messages. Because the index size is limited by your browser’s web storage capacity, this date will be updated as new emails arrive in your inbox to ensure the most recent messages can be searched.

Understanding the index

Because your index is stored on your device rather than on Proton’s servers:

You need to create a separate index on each device and in each browser you use to access Proton Mail.
If you sign out of your Proton Mail account on the web or on the desktop app, your index will still be there the next time you sign in on that device.
If you clear your browser data, your index will be erased. You can clear your browser data manually, or go to Settings → Clear browser data in the Proton Mail web app or Settings → Clear application data in the desktop app.
On the web, you may not be able to search message content in private browsing/incognito mode because browsers limit access to web storage. We recommend using content search in normal browsing mode only.

How to disable search message content

To temporarily disable email search:

Click in the Search messages box at the top.

Turn off the Search message content switch.

To delete the index of your emails from your web storage, you need to clear your browser data by clicking Settings → Clear browser data in the web app, or Settings → Clear application data in the desktop app.

If you want to search the contents of your messages again, you’ll need to enable search message content again by following the steps above.

Troubleshooting content search

You may see the following error messages:

“Content search cannot be enabled in this browser. Please try another browser.”

Your browser doesn’t support web storage. Please use one of our recommended browsers instead.

“Please activate your content search again.”

Your index is no longer valid or has been corrupted. To rebuild the index:

1. Clear your browser data by clicking Settings → Clear browser data (in the desktop app, Settings → Clear application data).

2. Enable search message content again by following the steps above.

Searching email content on iOS, iPadOS, and Android

In the Proton Mail apps for iOS, iPadOS, and Android, the index of your emails is stored on your device. Content search is off by default, so to use the feature, you must turn it on.

How to enable content search on mobile

1. Open the sidebar (three horizontal lines icon at the top left) and tap Settings.

2. Go to Preferences → Email content search.

3. Toggle the Email content search switch on.

The app will start to index your emails. This process may take a few minutes and can be quite resource-intensive. If you wish, you can Pause it at any time.

The index size is usually only a few MBs. To save your mobile data allowance, you can download emails for indexing over WiFi only. To do this, toggle the Allow download via mobile data switch off.

Once indexing is complete, your search results will include matches in the content of your messages. Your index updates automatically while Proton Mail is open. If your device runs out of storage, indexing will pause until more space becomes available.

Understanding the index on mobile

You need to create a separate index on each device you use to access Proton Mail.
If you sign out on the mobile app, the index is deleted and will need to be rebuilt if you wish to use the feature again.
If you uninstall the Proton Mail mobile app, or clear its data or storage in your device’s settings, your index will be erased.
To erase the index manually, go to Settings → Preferences → Email content search → On this device → Clear local search index.

How to disable content search on mobile

Turning off content search doesn’t erase your index. To erase it, see Understanding the index on mobile above.

Open the sidebar (three horizontal lines icon at the top left) and tap Settings.
Go to Preferences → Email content search.
Toggle the Email content search switch off.

Indexing stops or doesn’t finish on Android

Some Android manufacturers limit what apps can do in the background to save battery. This can pause or stop indexing when Proton Mail isn’t open on screen.

To fix this, keep Proton Mail open until indexing is complete, or allow Proton Mail to run in the background in your device’s battery settings. The steps depend on your phone’s manufacturer. For instructions for your device, visit Don’t kill my app(new window).

Content search privacy and security

The index is created on your device and only you can decrypt it when signed in to Proton Mail. This means no one else, including Proton Mail, can read the contents of your index.

It also means that when content search is turned on but Proton Mail isn’t open (in your browser, the desktop app, or the mobile app), someone with physical access to your device can’t read the contents of the index.

While you’re signed in and Proton Mail is open, a decrypted version of the index is held in your device’s memory. But anyone with access to your device at that point could read your emails directly anyway.

For more information on protecting your local data, see our threat model or our article explaining how to secure your data(new window).

Searching email content with Proton Mail Bridge

You can also search the contents of your emails on your desktop device by decrypting your messages and downloading them to a third-party email client with Proton Mail Bridge.

You can then search your message contents locally using your email client’s built-in search functions.

Advanced search

You can use the advanced search feature in the Proton Mail web app to search your emails by:

Subject (by searching for a keyword that is in the subject of the email)
Email address (Sender or Recipient)
Folder location (Inbox, Drafts, Sent, Archive, Spam, Trash, or custom folders)
Sent or received date

If you want to search the contents of your emails, you’ll need to:

Enable search message content using the steps above, or
Download Proton Mail Bridge to search within the third-party email client of your choice

How to use advanced search

To perform an advanced search in the Proton Mail web app, click in the Search messages box and select More search options.

The advanced search fields include:

Search messages: Enter your search keywords here.
Search in tabs: Choose whether to search within All mail, or your Inbox, Drafts, or Sent folders. Select the Other dropdown menu to choose another folder in your account, such as Starred, Archive, or a custom folder.
Date From and To fields: Search for emails sent or received within a specific time frame.
Sender and Recipient fields: Search for emails sent from or received by a specific person by searching their name or email address.
Address: Choose All or a specific address to include in your search.

Choose any combination of the above fields and click the Search button.

For example, you can look for emails in your inbox received within a specific time period, from a particular sender, with certain keywords in the subject (or contents if you’ve enabled search message content).

How to search using advanced syntax

Proton Mail also supports complex searches using advanced syntax for power users. Advanced search syntax works in the Proton Mail web app and our mobile apps for Android and iPhone/iPad.

But you can’t use advanced syntax to search message content. To use advanced syntax, you need to disable search message content.

Special characters can be used to execute complex logic when performing searches on your message metadata (the Subject, To/CC/BCC, and From fields). The logical AND is implicit between any two search keywords (searching for “hello world” means match “hello” AND “world”). The other search operators are listed in the table below.

Name	Operator	Example	Example Explanation
Logical OR	\|	hello \| world	Matches text containing hello or world
Logical NOT	! or –	hello !world	Matches text with hello but not world
Grouping	()	(cat -dog) \| (cat mouse)	Matches text with cat and without dog or cat with mouse
Phrase	“”	“hello world”	Matches text with the keywords adjacent and ordered, such as hello world and hello world and universe but not hello brave new world. You may use * as a word placeholder — *hello * world would match hello brave new world**
Proximity	“”~N	“hello world”~10	Matches text containing hello and world with less than 10 words between them
Quorum	“”/N	“hello dear world”/2	Matches text with at least 2 of the 3 words, such as hello dear and hello world. hello there would not match, but hello there world would
Order	“<<	hello << world	Matches text with hello and world only if they appear in the specified order. hello world would match but world hello would not
Start	^	^hello	Matches text that begins with hello, such as hello world but not say hello
End	$	world$	Matches text that ends with world, such as hello world, but not world peace
Wildcards	* and ?	h?llo w*d	The ? operator matches any single character, while * matches zero or more characters. The example search would match hello world as well as hallo word