I’ve argued strongly for the category of notes apps as the ideal home of your personal knowledge library, which I call a “second brain.”

1. Searchability: type in a few characters and see everything that matches, regardless of where it’s located
2. Duplication: duplicate your files, either to back them up, or create a new version while retaining the original
3. Access anywhere: keep files synchronized across devices, so you can access your files anywhere
4. Shareability: share a file with a friend or collaborator without losing your own copy
5. Editable: edit or change the content of your files, including the text, the formatting, the structure, and other elements
6. Upgradability: add or enhance functionality to your notes over time, as new features come out
7. Transferable: content can be moved from one place to another, through copy-and-paste for example
8. Linking: you can add clickable links, either to other files, or to external websites
9. Multimedia: save a wide variety of kinds of media, including text, images, videos, links, PDFs, and others
10. Meta-data: many pieces of data about your notes, such as location, date, device, and size, can be recorded automatically by software
11. Automation: certain kinds of content can be captured automatically, such as social media posts, emails, and web bookmarks

But this still leaves dozens of options, and it can be difficult to know exactly what the essential features look like. This article will describe what I believe to be the essential features for any app to serve effectively as your second brain, according to the methods I teach in my online course Building a Second Brain.

Here’s the summary:

Deal breakers

• 1. Quick capture and editing
• 2. Scales to thousands of notes without performance lag
• 3. Basic formatting options
• 4. Strong search feature
• 5. Ability to handle images and attachments
• 6. Private space, with public sharing

Must-haves

• 7. At least 3 levels of hierarchy
• 8. Many ways to capture information
• 9. Native and web versions
• 10. Capturing and syncing across multiple devices
• 11. Exportable as plain text

Nice-to-haves

• 12. Side-by-side viewing
• 13. Bullets or lists
• 14. Automatic date stamps
• 15. Tags

Deal breakers

1. Quick capture and editing

My most fundamental test of a knowledge capture app is whether, if you’re walking down the street and a brilliant (or wacky) idea suddenly pops into your mind, you will actually pull out your phone and capture it.

This is a common daily occurrence for photos, but not so much for ideas and insights. I can’t imagine this happening with Google Docs, or other heavy-duty text editing apps. One of the key strengths of notes apps is that they are made for just this kind of quick capture.

The same is true for editing – you need to be able to quickly find a note you’ve already saved, and opportunistically add, remove, or edit it, on a mobile device if necessary.

2. Scales to thousands of notes without performance lag

One of the critical principles for building a second brain is that each note should contain information from only one source. Instead of giant Microsoft Word or Google Docs documents, each note should be small and agile, so it can easily be mixed and matched with other notes.

This principle inevitably leads to creating thousands of notes in a relatively short amount of time. It’s very important that the collection can scale quickly, without performance lags.

3. Basic formatting options

Basic formatting options (such as bold, italics, underline, font colors, and highlighting) are an essential feature for quickly annotating text in a notes app. They are both very familiar for anyone who has done word processing, and customizable for those of us using specialized methods (such as my progressive summarization technique).

It doesn’t matter exactly which formatting options are available, but I recommend at least 3 distinct options that can be overlaid on top of each other (as in, a given passage can have more than one formatting style applied). I use bold, highlighting, and underlining, but any of these can easily be substituted for another style. What matters is that you use them consistently.

4. Strong search feature

With thousands of notes spanning hundreds of projects and topics, search is an essential feature of a notes app. Even with the powerful organizational methods I teach, it is often the very best way to go straight to the note you’re looking for.

It is essential that the search feature searches both the body of the note, as well as its title and meta-data. Ideally, the search feature also includes auto-complete (making suggestions as you type).

5. Ability to handle images and attachments

Although text tends to be the most common format for ideas, learnings, and observations, images are becoming a more and more important part of our creative vocabulary.

Your notes should be able to include images within the body of the note, not as an attachment that you have to click to view. This ensures that you will regularly come across them, serendipitously making new associations and connections.

Other kinds of files, such as videos, GIFs, PDFs, sound files, webpages, and others, should also be included, as attachments if necessary.

6. Private space, with public sharing

It’s important that your notes app serve as a private space for the ides that you’re not ready to share with the world. You should be able to jot down the most random thoughts, write out long personal reflections, sketch crazy harebrained schemes, all without the fear of criticism.

At the same time, it’s just as important that you have a way to share those ideas as soon as they’re ready for showtime. You can always copy and paste something to social media, of course, but ideally you’ll have a share feature integrated directly into the app you use. The less friction there is in sharing, the more often you’ll do it.

Must-haves

7. At least 3 levels of hierarchy

Although this is a strict requirement for my P.A.R.A. organizational method, I believe that in general at least 3 levels of hierarchy are needed for anyone to properly organize a large number of notes. In Evernote, the 3 levels are individual notes, which are contained in notebooks, which are contained in stacks. Other notes apps may use folders instead of notebooks, but the important thing is that you can put a group of related notes in one place, and they’ll stay there.

Numerous studies have shown that, despite the prevalence and effectiveness of search, people still overwhelmingly prefer to navigate through discrete containers to find their files. I believe this satisfies our sense of spatial awareness, and also provides many opportunities for serendipity (like wandering through the stacks of a library).

8. Many ways to capture information

Because we are using a notes app as a “universal inbox,” it is important that there are many different ways to get data into it.

Evernote, for example, has numerous options for importing content:

• Web clipper (for capturing web pages)
• Menu bar helper (for access through the computer menu bar)
• Email capture (a customized email address you can forward emails to to be captured)
• Mobile apps on popular platforms
• Dropping files on dock icon (Mac only)
• Copy and paste
• Click and drag into a note
• Third-party integrations (such as Bookcision for Kindle highlights, and IFTTT and Zapier for almost anything else)

Think about the 2 or 3 most common kinds of information you tend to save, and make sure you have a frictionless way to do so with the notes app you use.

9. Native and web versions

Many apps have gone web-first, meaning that they expect you to access them primarily through a web interface. This approach has many benefits, but it doesn’t work for notes apps. Your greatest enemy is friction, and the wait times for loading and reloading web pages are simply too long to keep up with creative ideation.

It is important that your notes app have a web version, to be able to access your notes from other computers, but your primary access will be through a native app. If there is also a native desktop app, this also allows offline access to your notes, and a way to save local backups.

10. Capturing and syncing across multiple devices

We live in a multi-device world, and this feature is now a must-have. You might capture most of your notes on a desktop computer, but having a mobile app for photos and videos will add a lot of richness and depth to your collection of notes. Reading ebooks on an iPad, I find that having my notes app just a few taps away is invaluable for capturing my ideas.

Although some apps allow you to set up sync manually, using third-party services, I don’t recommend it. Leave this technically complex task to the experts, even if you have to pay a monthly subscription.

11. Exportable as plain text

As heavily as I rely on formatting, I believe it is important to at least have an option for exporting notes as plain text. To protect against catastrophic data loss, the company going out of business, or simply because your needs change and a different app better suits your needs.

Plain text is the tool of last resort for getting your data out of a piece of software. These should be individual files, not a single, giant database record.

Nice-to-haves

12. Side-by-side viewing

This might seem overly specific, but is actually a crucial part of using your notes to do creative work. Being able to compare and contrast two notes, and move information between them if needed, is essential for creative synthesis. This can be accomplished through multiple panels, or by allowing you to open notes in separate windows.

13. Bullets or lists

Lists are one of the easiest ways to brainstorm and plan, and a natural fit for informal notes. Although a list can simply be a series of text entries without any particular structure, it’s helpful if there is a bullet, numbering, or list feature that makes it easy to create them.

14. Automatic date stamps

Within notebooks or folders, the best way to organize groups of notes is by their date of creation. Our brains naturally understand the flow of time, and often associate ideas with specific events or periods of time. Choose a notes app that automatically labels each note with the date.

15. Tags

Although I am a critic of using tags as a primary organizational system, they are still valuable. Your notes app should allow you to create and apply multiple tags to any given note, giving you an extra layer of control.

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