An ER diagram maker that presents your schema step by step
- Free
- No sign-up
- Works offline
Entities, attributes, and crow's-foot relationships — drawn in your browser, kept on your device, and narrated on demand.
Present reveals your ER diagram one step at a time, on its own.
Diagramium is a free, browser-based ER diagram maker: draw entities, attributes, and crow's-foot relationships, then press Present and the finished schema reveals itself step by step with optional AI voice narration. No account is needed to draw, present, or export a PNG or SVG.
It is also local-first. Diagrams live on your device and in the files you export — nothing is uploaded, and a lost connection does not stop the editor once it has loaded. Backend developers use it to sketch a schema before writing migrations, students use it to learn database design, and analysts use it to map the tables behind a report.
Entities, attributes, and crow's-foot cardinality
An ER diagram shows three things: entities (the tables), attributes (the facts each table holds), and relationships whose end markers — crow's-foot notation — state how many rows on each side can take part. The markers are a small alphabet worth learning once:
- A single stroke means exactly one.
- A circle means zero — the relationship is optional.
- The three-pronged crow's foot means many.
- Markers combine: a circle beside a crow's foot reads as "zero or many".
A one-to-many relationship means one row in the first table can link to many rows in the second, while each of those rows points back to exactly one — one customer places many orders. A many-to-many relationship means rows on both sides can link to many on the other — a student enrolls in many courses and each course holds many students — and a physical schema resolves it with a junction table. For a worked example from blank page to finished schema, read how to create an ER diagram.
Present the schema, table by table
Press Present and the schema tells itself in order — entity by entity, with optional AI voice narration, subtitles with word-by-word highlighting, and a spotlight on the shape being discussed. Each step can carry its own speaker note — a "why this matters" insight — so the diagram does not just show that orders links to customers, it says why the foreign key sits where it does.
That turns a schema review from a static picture into a walkthrough: the reveal order is the argument, one table at a time. You can also record the presentation live as it plays. Switch the theme to a hand-drawn Doodle sketch for a whiteboard feel, or keep a classic professional palette for documentation.
How to make an ER diagram, start to export
- Open the ER editor at diagramium.com/er. It runs in the browser — nothing to install, no sign-up.
- Add an entity for each table and give it the table's name.
- List each entity's attributes — the columns you expect to store.
- Drag a connector between two entities to create a relationship.
- Set the crow's-foot marker on each end so the line states its cardinality: one-to-one, one-to-many, or many-to-many.
- Press Present to preview the step-by-step reveal, and add a speaker note wherever a design decision needs a word of explanation.
- Export as PNG or SVG — or create a free account to export the presentation as an animated GIF, video, or animated SVG.
ER diagram, UML class diagram, or data flow diagram?
An ER diagram models data at rest — the tables a database will hold and how their rows relate — which makes it the right pick when the deliverable is a schema. Its two neighbors answer different questions. A UML class diagram models code structure: classes carry methods and inheritance, not just stored facts, so reach for it when you are designing objects rather than tables. A data flow diagram models data in motion — how information moves between processes and stores — so it explains a pipeline, not a schema.
Diagramium includes separate editors for all three, among 27 diagram types in one app, and the Explore gallery holds hundreds of ready-made, editable examples to start from.
Free, private, and offline
Diagramium is free, carries no ads and no analytics scripts — the sole telemetry is an anonymous per-diagram count, and diagram content is never collected. There is no paid tier: a free account exists only to unlock the animated export formats.
Because the app is local-first, your schema never leaves your machine unless you export a file and share it yourself, and the editor keeps working offline once it has loaded. Any published diagram from the gallery can also be embedded on another website as a self-playing iframe, so a narrated schema can live inside your team's docs.
Frequently asked questions
Is this ER diagram maker free? Do I need an account?
Diagramium is free and there is no paid tier. You can draw, present, and export PNG or SVG images of your ER diagram without any account; a free account is only needed to unlock the animated export formats — GIF, video, and animated SVG.
What formats can I export an ER diagram to?
You can export any ER diagram as PNG or SVG with no account. Animated GIF, video, and animated SVG exports unlock with a free account, and you can also record a presentation live while the diagram plays itself.
Does the ER diagram maker work offline, and where are my diagrams stored?
Your ER diagrams are stored on your own device and in the files you export — Diagramium is local-first and never uploads diagram content. Once the app has loaded in your browser, it keeps working offline.
What do the crow's-foot symbols on an ER diagram mean?
In crow's-foot notation, each end of a relationship line carries a marker: a single stroke means exactly one, a circle means zero (the relationship is optional), and the three-pronged crow's foot means many. Markers combine, so a circle beside a crow's foot reads as "zero or many".
What is the difference between one-to-many and many-to-many?
In a one-to-many relationship, one row in the first table links to many rows in the second, but each of those rows points back to exactly one — one customer, many orders. In a many-to-many relationship, rows on both sides can link to many on the other — students and courses — and a physical schema resolves it with a junction table.
Should I draw an ER diagram or a UML class diagram for my database?
Draw an ER diagram when the deliverable is a database schema: it models tables, columns, and row-level cardinality. Draw a UML class diagram when you are modeling code, where classes carry methods and inheritance. Diagramium includes separate editors for both.
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