Introducing GanttBuilder: A Free Gantt Chart Tool That Runs in Your Browser
Every other Gantt tool wants your email, hides features behind a paywall, and stores your project data on their servers. I built one that does none of those things — and put it on the web for free.
Meet GanttBuilder: a complete project-scheduling tool that lives in a single HTML file and runs entirely in your browser. No account. No installation. No backend.
-->The problem with modern Gantt tools
If you've shopped for a Gantt chart tool recently, you've probably noticed a pattern:
- Sign up to see anything. Most "free" tools demand an email before they'll even show you the interface.
- Project limits. Free tiers cap you at 3 projects, 10 tasks, or a 30-day trial.
- Your data on their servers. Project schedules often reveal sensitive information — deadlines, partners, internal milestones. Most tools store all of it on their cloud.
- Bloat. Modern PM platforms are giant apps with chat, time tracking, dashboards, and AI features you don't need just to draw bars on a timeline.
For a solo planner, freelancer, or small team that just wants a clean chart, this is overkill. So is paying $10–$50 per user per month for software you'll use occasionally.
What GanttBuilder does differently
GanttBuilder is a single HTML page. You open it. You start typing. That's the entire onboarding.
- No signup. There's nothing to sign up to. The "server" is your browser.
- No installation. Works in Chrome, Firefox, Safari, Edge — any modern browser.
- Works offline. After the first load, you can save the page and use it without internet.
- Your data stays put. Everything saves to your browser's
localStorage. We have no servers to send it to. - It's free. Forever. No "free tier", no upsell, no premium plan. The whole thing is open code you can read, fork, and self-host.
Try it now (live demo)
Below is the actual tool running inside this post. Click Load Sample to see a 24-task example, then edit any cell — the chart updates in real time.
If the embed doesn't fit your screen, open the full version in a new tab.
Six features that make it actually useful
1. Working-day scheduling
Enter a duration in days, and GanttBuilder treats it as working days. Saturdays and Sundays are excluded automatically. If a task starts on a weekend, it rolls to Monday. No manual calculation.
2. Predecessor chains
Enter a predecessor task number, and the start date computes automatically: next working day after the predecessor finishes. Change one duration, and everything downstream re-schedules instantly. Multiple predecessors? Just separate with commas (5,8) — it waits for whichever finishes later.
3. Hierarchical tasks with auto roll-up
Indent rows to create parent-child relationships. Leave the parent's duration blank, and it automatically rolls up to min(child starts) through max(child finishes). The summary bar updates as you add or change children.
4. Classic, print-friendly look
The default style mirrors the traditional 3-row date header (Month / Day / Weekday) found in MS Project and Primavera. Bordered task table on the left, dependency arrows in the chart, weekend shading. Designed to look right on an A3 printout, not just on a screen.
-->5. Single-file HTML export
Click Export HTML and download a self-contained file (about 30–80 KB). It has no external dependencies — open it in any browser, anywhere. Attach to email. Upload to your blog. Embed in an iframe. Print to PDF.
6. Privacy by architecture
Most "private" tools are private by policy — they could collect your data, they just promise not to. GanttBuilder is private by architecture: there's no backend to send data to. It literally cannot phone home.
How to make your first chart in 30 seconds
- Open the builder
- Click Load Sample to see a working example
- Click any cell to edit — change task names, durations, predecessors
- Use the indent buttons (− / +) to create sub-tasks
- Click Export HTML to download your chart
That's it. The chart auto-updates as you type. There's nothing else to learn.
What it's good for
Projects I've seen people plan with it:
- Engineering / fabrication schedules — equipment manufacturing with drawings, materials, fabrication, inspection, delivery phases
- Software release timelines — sprints, code freeze, QA, launch
- Research and thesis planning — lab work, writing, advisor reviews, submission
- Event planning — wedding timelines, conference logistics, product launches
- Consulting deliverables — discovery, analysis, milestones
- Home renovation — demolition, electrical, plumbing, finishing in sequence
Anything where steps need to happen in order, with deadlines, is a candidate.
What it doesn't do (yet)
Some things on the roadmap:
- Public holidays. Currently skips weekends only — national holidays need manual adjustment.
- Baseline comparison. Plan vs. actual is a workaround right now (separate rows).
- Resource leveling. No per-person allocation tracking.
- Real-time collaboration. Local-first by design; team workflows use CSV via Git or Drive.
- Lag/lead times on dependencies.
If those matter for your workflow, a SaaS tool like Asana, Monday.com, or ClickUp is a better fit. For everything else, GanttBuilder is enough.
How it's structured (for the curious)
The whole tool is one HTML file with three sections:
- An editable task table (input fields per row)
- A live SVG chart that re-renders on every edit
- A tiny scheduling engine that computes working-day math + dependency resolution
About 1,200 lines of JavaScript total. No framework. No build step. View source, edit, host your own copy.
The point
The web used to be full of small tools that did one thing well. Somewhere along the way, every utility became a SaaS, every SaaS became an account, and every account became a database of your behavior.
This is a small attempt to push back. Open the tool, make a chart, close the tab. We're not following you.
-->Try it now
Questions? Read the complete user guide, or check the next post on what a Gantt chart actually is and when to use one.