A generation of pioneers (Doug Engelbart, Ted Nelson, Alan Kay, and many more) saw the computer as tool to augment human problem-solving by giving people power over information.

Today, that information mostly remains siloed across tools. Take cloud-based document editors, where pages are their smallest atomic unit. Information is locked inside of pages and files and folders — that’s reminiscent of how things were done a century ago.

We built Notion on a framework that allows information to stand on its own, free from any constraint or container, instead putting the power in the hands of the user at a granular level. That framework is built on blocks.

Everything you see in Notion is a block. Text, images, lists, a row in a database, even pages themselves — these are all blocks, dynamic units of information that can be transformed into other block types or moved freely within Notion. They’re the LEGOs we use to build and model information. And when put together, blocks are like LEGO sets, creating something much greater than the sum of their parts.

This flexibility is at the heart of Notion’s mission. While blocks require our engineering team to apply extreme rigor when structuring information, we wanted an atomic, graph-like data model to provide our users with the ability to customize how their information is moved, organized, and shared.

The block model makes Notion unique, and it’s the foundation for how Notion thinks about bringing to life what pioneers thought computing, as a medium, could become.

Much like LEGO blocks in a LEGO set, Notion blocks are the singular pieces that represent all units of information inside the Notion editor. The attributes of a block determine how that information is rendered and organized.

Every block has the following attributes:

• ID — each block is uniquely identifiable by its ID. You can see the ID of page blocks at the end of the URL in your browser. We use randomly-generated UUIDs (UUID v4) for IDs in Notion.
• Properties — a data structure containing custom attributes about a specific block. The most common property is title, which stores the text content of block types like paragraphs, lists, and of course, the title of a page. More elaborate block types require additional or different properties, like a page block in a database with user-defined properties.
• Type — every block has a type, which defines how a block is displayed, and how the block’s properties are interpreted. Notion supports many types of blocks, most of which you can see in the “new block” menu that appears when you press the + button or in the / menu:

In addition to the attributes that describe the block itself, every block has attributes that define their relationship with other blocks:

• Content — an array (or ordered set) of block IDs representing the content inside this block, like nested bullet items in a bulleted list or the text inside a toggle.
• Parent — the block ID of the block’s parent. The parent block is only used for permissions.

Like LEGO blocks, Notion blocks can be combined with other blocks to make something much more powerful — like a roadmap that’s been totally customized to your team’s process, tracking progress and holding all project information in one place. We organize all aspects of blocks to make sure they do the right things and live in the right places, enabling users to connect them and further tailor Notion to solve their problems.

The block type is what specifies how the block is rendered in Notion’s UI — and depending on that type, we interpret the block’s properties and content differently. You may be familiar with this if you've used the Turn into function in Notion, which allows you to turn one block type into another.

Changing the type of a block doesn’t change the block’s properties or content — it only changes the type attribute. The information is just rendered differently, or even ignored if the property isn’t used by that block type.

For example, you can see here that a To-do list block is transformed into several other block types. We also check that To-do list item. The “checked” property of the To-do list block is ignored when the block is transformed into Heading and Callout block types — but by the time we come full circle to turn the block back into a To-do list block, it is still checked.

changing_blocks.mp4