ERD Generator — Entity-Relationship Diagrams from SQL
Generate text-based and Mermaid ER diagrams from SQL CREATE TABLE statements with automatic relationship detection.
How it works
- 1Paste or type your text in the input field
- 2Click "Generate ERD" — processing happens in your browser
- 3Copy the result or download as a text file
What to do next
About ERD Generator
ERD Generator is a free, in-browser developer tool. Generate text-based and Mermaid ER diagrams from SQL CREATE TABLE statements with automatic relationship detection. The page exposes a small surface — input, controls, output — so a first-time visitor can complete the job without reading documentation.
Typical users of ERD Generator include students learning new languages, frontend developers prepping fixtures and engineers debugging API payloads. The thread connecting all of them is the same: a focused developer utility task that fits cleanly into a browser tab and benefits from a tool with sensible defaults and minimal setup.
ERD Generator parses your file with standard browser APIs entirely inside the browser, applies the options you selected, and returns a download. The processing has no network step, which means a slow or intermittent connection does not slow down the work — once the page is loaded, only your CPU and RAM are involved.
From a technical standpoint, ERD Generator is JavaScript and standard browser APIs running in your tab. The browser is the runtime; the page is the interface. Maximum input size: 0 MB per run.
Most people land on ERD Generator via a search at the moment they actually need the tool. That shapes the design: the page is a single screen with the input on one side, the controls in the middle, and the result on the other, so a first-time visitor can complete the job without reading documentation.
Even on its own, ERD Generator composes well with the rest of your toolkit. The output is a standard developer file that opens in any program that handles the format, so the result of one run can become the input to whatever step you use next.
The output handed back by ERD Generator is the output file. If you would prefer to keep the result in the browser instead of downloading it, you can copy it from the result panel and paste it directly into another tab — useful when the next tool in your workflow expects pasted text rather than a file.
The only practical limit is the 0 MB per-file ceiling, which keeps the tool responsive across a wide range of devices. Run the tool ten times in a row, run it ten thousand times — it behaves the same way and produces the same quality of result.
Some notes on the design of ERD Generator. The page is intentionally narrow: one input, the controls relevant to the task, and one output. Adding unrelated features would make the common case slower for the majority of users, so the surface is held to what people actually use.
A short note on how ERD Generator came to look the way it does: every iteration started by watching how someone unfamiliar with the tool actually used it, then removing whatever got in their way. That is why the upload area dominates the screen, the run button is bigger than the secondary controls, and the result panel is unmissable when the job finishes.
Tips from users who reach for ERD Generator regularly: process one input first to confirm the settings produce what you expect before committing to a batch; treat the page as the working surface and avoid leaving large jobs running in a backgrounded tab where the browser may throttle JavaScript; and if a particular file fails, check whether the source is intact by opening it in its native viewer — most "tool errors" are actually input errors.
For most failure modes, refreshing the page and re-running the job is enough — the engine has no persistent state to corrupt. If the same input fails twice in a row, the input itself is most likely the problem (a truncated file, an unexpected variant of the format, or a stream the engine does not recognise).
As a single-page tool, ERD Generator stays focused on one developer utility step. Multi-step workflows are composed by chaining adjacent tools — each tool produces a standard file the next one can read directly, so a longer pipeline is just a sequence of short tab-and-tab visits.
ERD Generator is one of many single-purpose tools in the catalog. Each is built around the same single-page model. Use this one, close the tab, and come back the next time you need the same job done. None of the tools require prior knowledge of the others — each page is self-contained.
How it works
- 1Reach the ERD Generator page in your browser to begin.
- 2Add your developer input by dropping it onto the page or browsing for it.
- 3Tweak the controls if the defaults are not quite right for your input. The options are kept short and labelled in plain language.
- 4Hit the run button. standard browser APIs does the work in your browser tab.
- 5Save the output when it is ready.
- 6Repeat the process for additional inputs whenever you need to. The page stays loaded, so subsequent runs are quick.
Common use cases
- Compare two API responses to spot a regression using ERD Generator.
- Inspect a regex against a test string before committing it.
- Hash a string for a quick reproducibility check.
- Generate a quick fixture without leaving the browser.
- Inspect a payload during local development without writing a script.
- Decode a token to confirm its claims during a debugging session.
- Pretty-print a minified blob during incident triage.
- Encode binary content for transport in a JSON body.
- Validate a config blob before pushing to staging.
- Generate boilerplate from a single specification line.
FAQ
How are relationships detected?
The tool parses REFERENCES clauses in column definitions to identify foreign key relationships between tables.
What is Mermaid format?
Mermaid is a text-based diagramming language that can be rendered into graphical ERDs by tools like GitHub, GitLab, and mermaid.live.
Can I render the Mermaid output?
Yes — paste the Mermaid erDiagram syntax into mermaid.live, GitHub markdown, or any Mermaid-compatible renderer.
Does it show cardinality?
Foreign key relationships are shown as one-to-many by default, which is the most common relationship type.
Is my schema private?
Yes — parsing and generation run entirely in your browser.
What if I have no foreign keys?
Tables will be shown without relationships. The entity listing still displays all columns and types.
Can I use ERD Generator offline?
Once the page is loaded, ERD Generator can complete jobs without an active internet connection — the engine is bundled with the page, so there is no per-job network call. The initial page load does require a connection (to fetch the static assets), but after that you can disconnect entirely and the tool will still work. This is a side-effect of the local-first architecture, not a deliberate "offline mode" feature.
How do I run ERD Generator over a folder of files?
ERD Generator processes one input at a time by design — it keeps memory usage predictable on lower-end devices and makes results easier to verify. To handle a folder, run the tool once per file; the page stays loaded between runs and remembers your last-used settings, so the second run is essentially instant.
Can I trust the output of ERD Generator for important work?
ERD Generator is built on standard browser APIs, which is the same class of engine used by professional developer utility pipelines. For deterministic operations, the output is byte-identical to what an equivalent CLI run would produce; for operations involving a codec or a model, the result is well within the range of what comparable tools generate. If you have a specific reference output you need to match, run a small test job first to confirm the configuration produces what you expect.
Can I use ERD Generator on documents that contain personal data?
Your file is processed inside your browser by standard browser APIs. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
Does ERD Generator ask for any browser permissions?
ERD Generator only needs the standard web platform — file picker access for the inputs you choose to load, and optionally clipboard access if you copy the result rather than downloading it. There is no microphone, camera, geolocation or background-permission request, because none of those are needed for the work the tool does.
Can ERD Generator run inside a corporate firewall?
ERD Generator is a static page running an open-source engine in your browser, so a typical corporate firewall does not get in the way as long as it allows JavaScript to load from Favtoo. For teams that need to host it themselves on an internal network, the underlying engine (standard browser APIs) is open-source and can be packaged into a private build with the same behaviour. Reach out via the Contact page if that is something you are exploring.
How long does ERD Generator take to process a file?
Most jobs finish in seconds. Speed scales with input size and with how many CPU cycles your browser tab has available — the engine runs in your browser, so it shares resources with whatever else you have open. For inputs near the 0 MB ceiling, expect anywhere from a few seconds to roughly a minute on a typical laptop. Closing other heavy tabs noticeably speeds things up.
Will ERD Generator ask me to pay to download the result?
ERD Generator is free to use. The processing runs in your browser, which keeps the per-user cost low enough that the tool can be offered openly. The download is the same file the engine produced — you can use it for as many runs as you need.