
A diagram can save hundreds of words. Making a diagram efficient and engaging isn’t easy. There are many tools available to facilitate the diagram development process. However, many diagrams bring less excitement to work with and view as the final result. In this article, I will share 4 free fantastic diagramming tools to make yours stand out.
Excalidraw: Hand-drawn Diagraming
Excalidraw is a unique online tool to transform the feeling of your drawing. To get started, go to their website without providing sign-in or additional information about yourself.
It feels pre-installed with Microsoft Paint, and it is even much simpler than that. By default, you only have three shapes: rectangle, diamond, and circle.
In the diagramming part, you need to draw many things out. Unlike other tools that provide your template, it’s more involved with the user. You’d need to draw more in Excalidraw.
Another great thing about Excalidraw is that you can use the icon shared by the community. The frequently used ones are AWS, GCP, and Azure, all available in the community library. For data professionals, I found this one has been used by many people, the one named Data Platform, created by Bach Chu.
I used Obsidian for my personal knowledge management. Excalidraw is a plugin to add to Obsidian, which can further boost your productivity or draw your ideas on a white canvas.
Below is the diagram I use this library to show how it looks like:

Recommendation for Excalidraw if you are looking for
- hand-drawn feeling diagram
- comfortable with some basic drawing or eager to draw a more complex diagram
- simple access and no sign-on needed.
Mermaid: Diagramming as Code
Many tools to make diagramming are UI based. It can be tedious to lay out everything and time-consuming to shuffle things around when some content requires updates. It also won’t scale very well when you need to draw a lot of similar diagraming.
Code is one of the resolutions for this diagramming problem.
Mermaid is a JavaScript-based library that creates diagrams and visualizations using text and code. The core idea of Mermaid is to define the diagraming you’d like to render by its Markdown-like code. Then Mermaid will draw rest for you.
The Mermaid syntax has some learning curves, and its expression is unique. However, if you use diagramming frequently, it’s worth investing the time to get familiar with its syntax since using code will save so much time in the long term.
Another great thing is that Mermaid is JavaScript-based. You can bring and share the diagram with others effortlessly. Some syntax highlighter is also able to render the Mermaid diagrams directly. For example, Obsidian can render Mermaid syntax and show the diagram correctly.
For the data project, Entity Relationship Diagrams (ERD) are used quite often. For instance, the following example drawed
---
title: Order example
---
erDiagram
CUSTOMER ||--o{ ORDER : places
ORDER ||--|{ LINE-ITEM : contains
CUSTOMER }|..|{ DELIVERY-ADDRESS : uses

Recommendation for Mermaid if you are looking for
- Code-oriented mindset and would like to express code to draw diagrams
- Scale drawing diagramming and save time in making changes to the diagram
To learn more about how to use Mermaid, I have written a story on it before.
Mastering Gantt Charts: Learn How to Build Them Using Code Alone
Learn how to master Gantt charts using code alone in project management tracking. Many UI-based tools for Gantt chart creation can take a lot of work to manage. Discover the elegant and practical approach of building Gantt charts with code to reflect fast-paced project changes in this insightful story.
Draw.io: The Comprehensive Option
Draw.io is such an excellent comprehensive option that works well for complex diagraming. It has an exhaustive list of selections to draw flow charts, UML, ERD, etc.
Draw.io integrates with Google drive smoothly. You can put all the diagramming into a shared folder and work seamlessly across devices.
One nice thing about this diagramming tool is that it automatically connects lines between shapes. Moving the shapes around will also carry all the connected lines to move together.
Suppose you want to have a hand-drawn diagramming style. Go to the “Style” type and choose “sketch.” It will apply the hand-draw theme for all the available common shapes.

Recommendation for Draw.io if you are looking for
- A comprehensive option with many available shapes and an imported library.
- Less worrying about work on different devices and opening to Cloud Drive as storage.
- Have experience with the diagramming tool before and want to have less learning curve
Google Slides or Mac Keynote: An Overlooked Option
Regarding diagraming, a free and handy tool almost everyone knows but overlooks when it comes to drawing diagrams — Google Slides or Mac Keynote is for more than just presentations or product demos.
This option is only considered in limited use cases. The misconception is that you don’t need a presentation to think about using those tools to draw diagrams. You can use Google Slides or Mac Keynote to create diagrams, and that could save you the effort of switching to another tool.
All we need to do is: remove all the text boxes and keep a blank canvas to start your diagram.
They are also backed by cloud storage — Google Drive or iCloud. So we don’t need to worry about losing them.
Both Google Slides and Mac Keynote have many shapes to choose from. One of the big advantages of using Google Slides and Mac Keynote is the ability to create animation with your diagram. You can further make a GIF with your diagram.
They are sufficient to make simple and good-looking diagrams with animation.

Recommendation for Google Slides or Mac Keynote if you are looking for
- You are familiar with Google Slides or Mac Keynote and may underestimate its diagramming ability
- Less worrying about working on different devices and opening to Cloud Drive as storage (You can work offline on Mac Keynote).
- You’ll need to create an animation
Final Thoughts
Diagramming is a fantastic way to illustrate an idea or complex concept. The most important thing is to make it more straightforward for the reader. I hope those 4 free excellent diagramming tools can make yours stand out.
Please let me know your feedback on this story.
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