I watched someone spend 45 minutes formatting a sales report. They had all the numbers in a spreadsheet. The layout was the same as last week. But they still had to copy data into a Word template, fix the alignment, recalculate the totals, and export to PDF. Every Monday.
That felt like a problem an API should solve. If the data is structured and the layout is fixed, the entire formatting step is deterministic. Send the data, pick a template, get a report.
That became ReportForge API.
What it does
Two endpoints, each taking structured data and returning a complete HTML report:
| Endpoint | Input | Output |
|---|---|---|
POST /api/csv-to-report | CSV string + template name | Styled HTML report + metadata |
POST /api/json-to-report | JSON array + template name | Styled HTML report + metadata |
Seven templates, each designed for a specific business use case:
| Template | Required Columns | Use Case |
|---|---|---|
sales-summary | item, amount | Weekly/monthly sales reviews |
expense-report | description, amount | Bookkeeping, reimbursement |
inventory-status | item, quantity | Warehouse management, reorder alerts |
invoice | description, amount | Client billing |
Every template also accepts optional columns that add detail when present: dates, categories, SKUs, tax rates, vendor names, client emails.
Try it right now
No signup needed. The free tier (5 reports/day) requires no API key.
Generate a sales summary:
curl -X POST https://reportforge-api.vercel.app/api/csv-to-report \
-H "Content-Type: application/json" \
-d '{
"csv": "item,amount,quantity,category\nWidget Pro,1250.00,50,Hardware\nGadget Plus,890.50,30,Electronics\nService Plan,2400.00,12,Services\nCable Kit,156.75,100,Accessories\nMonitor Stand,445.00,25,Hardware",
"template": "sales-summary",
"title": "Q1 Sales Report"
}'
Response:
{
"html": "<!DOCTYPE html><html lang=\"en\">...",
"meta": {
"template": "sales-summary",
"rowCount": 5,
"columns": ["item", "amount", "quantity", "category"],
"generatedAt": "2025-02-15T10:30:00.000Z"
}
}
Save the html field to a file, open in a browser, and you get a professional report with summary cards at the top (total sales, average sale, largest sale, transaction count), a formatted data table with currency alignment, and a totals row at the bottom.
Generate an invoice:
curl -X POST https://reportforge-api.vercel.app/api/json-to-report \
-H "Content-Type: application/json" \
-d '{
"data": [
{"description": "Web Development", "quantity": 40, "unit_price": 150.00, "amount": 6000.00, "invoice_number": "INV-2025-042", "client_name": "Acme Corp", "client_email": "[email protected]"},
{"description": "UI Design", "quantity": 20, "unit_price": 125.00, "amount": 2500.00, "invoice_number": "INV-2025-042", "client_name": "Acme Corp", "client_email": "[email protected]"},
{"description": "Project Management", "quantity": 10, "unit_price": 100.00, "amount": 1000.00, "invoice_number": "INV-2025-042", "client_name": "Acme Corp", "client_email": "[email protected]"}
],
"template": "invoice"
}'
The invoice template produces a document with a header (invoice number, date), a bill-to section (client name, email), a line items table (description, quantity, unit price, amount), subtotals, tax calculation, and payment terms.
Generate an expense report:
curl -X POST https://reportforge-api.vercel.app/api/csv-to-report \
-H "Content-Type: application/json" \
-d '{
"csv": "description,amount,date,category,vendor\nOffice supplies,234.50,2025-01-15,Office,Staples\nSoftware license,599.00,2025-01-18,Software,Adobe\nClient lunch,87.25,2025-01-20,Meals,Restaurant\nUber rides,45.60,2025-01-22,Travel,Uber\nCloud hosting,149.00,2025-01-25,Software,AWS\nPrinter ink,65.99,2025-01-28,Office,Amazon",
"template": "expense-report",
"title": "January Expenses"
}'
The expense template groups rows by the category column, shows per-category subtotals, and calculates the grand total. The summary cards at the top show the total and the top spending categories.
The template showcase
Each template is designed for a specific type of business report. Here is what they produce:
Sales Summary
- Summary cards: total sales, average sale, largest sale, transaction count
- Full data table with all columns from your data
- Currency formatting with tabular alignment
- Totals row at the bottom
Expense Report
- Rows grouped by category with category headers
- Per-category subtotals showing item count and total
- Grand total row
- Top spending categories in the summary cards
Inventory Status
- Stock level for every item
- Low-stock items highlighted in red
- Reorder alert banner when items are at or below reorder level
- Summary cards: total SKUs, total units, low-stock count, estimated inventory value
Invoice
- Invoice header with number and date
- Bill-to section with client name and email
- Line items table: description, quantity, unit price, amount
- Subtotal, tax (when
tax_ratecolumn is present), grand total - Payment terms section
All seven templates include:
- Clean, professional typography with system fonts
@media printCSS: proper page breaks, repeating table headers, fixed footers- Responsive grid layouts for summary cards
- HTML-escaped user data (XSS prevention)
- Timestamps in the footer
The architecture
Client request
|
v
Vercel Serverless Function
|
v
Auth check (API key → Supabase, or anonymous free tier)
|
v
Rate limit check (in-memory for free, per-key for paid)
|
v
Input size validation (100KB free, 2MB starter, 10MB business)
|
v
Zod schema validation
|
v
CSV parsing (if csv-to-report) or JSON validation (if json-to-report)
|
v
Template rendering (pure function: data[] → HTML string)
|
v
JSON response: { html, meta }
The template rendering step is pure computation. Each template function takes an array of objects and a title, runs calculations (totals, grouping, formatting), and returns an HTML string. No template engine, no external dependencies beyond Zod.
Why no template engine?
I considered Handlebars, EJS, and Mustache. The problem with all of them is that the logic in these reports is not trivial string interpolation. The expense template groups by category and calculates subtotals. The inventory template detects low-stock items and generates alert banners. The invoice template extracts metadata from the first row and handles tax computation.
With a template engine, this logic would either live in helpers (which is just JavaScript with extra steps) or in the template itself (which is hard to type-check and debug). Writing the HTML construction in TypeScript means the entire render pipeline is type-checked, testable, and debuggable with standard tools.
The trade-off is that the template code mixes HTML structure with logic. For fixed-layout reports, this is acceptable. For a system where end users customize templates, it would not be.
Why custom CSV parsing?
The CSV endpoint includes a hand-written parser that handles RFC 4180 quoting: quoted fields containing delimiters, double-quote escaping, and custom delimiter characters (set "delimiter": "\t" for TSV). This avoids adding a parsing library dependency.
Using it from different languages
JavaScript (Node.js) -- save report to file:
const res = await fetch('https://reportforge-api.vercel.app/api/csv-to-report', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({
csv: 'item,amount,quantity\nWidgets,1250,50\nGadgets,890.50,30',
template: 'sales-summary',
title: 'Weekly Sales'
}),
});
const { html, meta } = await res.json();
console.log(`Generated report: ${meta.rowCount} rows, ${meta.template} template`);
// Save to file and open in browser
const fs = await import('fs');
fs.writeFileSync('report.html', html);
Python -- generate and email an invoice:
import requests
response = requests.post(
'https://reportforge-api.vercel.app/api/json-to-report',
json={
'data': [
{'description': 'Consulting', 'quantity': 20, 'unit_price': 200, 'amount': 4000, 'client_name': 'Client Co'},
{'description': 'Development', 'quantity': 40, 'unit_price': 150, 'amount': 6000, 'client_name': 'Client Co'},
],
'template': 'invoice',
'title': 'February Invoice'
}
)
result = response.json()
print(f"Generated invoice: {result['meta']['rowCount']} line items")
with open('invoice.html', 'w') as f:
f.write(result['html'])
Google Apps Script -- weekly report from a Sheet:
function generateWeeklyReport() {
const sheet = SpreadsheetApp.getActiveSheet();
const data = sheet.getDataRange().getValues();
const headers = data[0];
const rows = data.slice(1).map(row =>
headers.map((h, i) => `${row[i]}`).join(',')
).join('\n');
const csv = headers.join(',') + '\n' + rows;
const response = UrlFetchApp.fetch(
'https://reportforge-api.vercel.app/api/csv-to-report',
{
method: 'post',
contentType: 'application/json',
payload: JSON.stringify({
csv: csv,
template: 'sales-summary',
title: 'Weekly Sales Report'
})
}
);
const result = JSON.parse(response.getContentText());
// Email the report or save to Drive
}
Pricing and limits
| Plan | Price | Reports/day | Max input size |
|---|---|---|---|
| Free | $0 | 5 | 100 KB |
| Starter | $9/mo | 100 | 2 MB |
| Business | $29/mo | Unlimited | 10 MB |
The free tier does not expire and is not a trial. Five reports per day covers weekly use for most small operations. The Starter tier is designed for businesses that generate reports daily. The Business tier is for automated pipelines that produce reports at scale.
Lessons from building two APIs
This is my second API product. The first, DocForge API, handles format conversion between Markdown, CSV, JSON, and YAML. Building ReportForge on top of that experience reinforced a few things:
1. Stateless serverless is the right fit for data transformation. No database connections to pool, no state to manage, no cache to invalidate. The function receives data, transforms it, returns the result. Vercel handles the infrastructure.
2. A free tier that works without signup removes friction. ReportForge lets you make 5 requests per day with no API key. You can evaluate the entire product from a curl command. Removing the signup step means people actually try it instead of bookmarking it for later.
3. Metadata makes APIs more useful for automation. Every ReportForge response includes the template name, row count, column list, and timestamp. This lets consumers validate the response programmatically without parsing the HTML.
4. Print CSS is an underappreciated feature. Adding @media print rules was a small amount of work that makes the output dramatically more useful. Reports that look good when printed to PDF are reports that actually get used.
What is next
Templates I am considering based on common business needs:
Project Status -- task list with status indicators, completion percentage, and timeline
Payroll Summary -- employee hours, rates, gross pay, deductions, net pay
Meeting Minutes -- agenda items, attendees, action items, decisions
Customer List -- contact directory with sortable columns and category filters
If you generate a type of report regularly that is not covered by these seven templates, I would like to hear about it.
Links
Live API + Demo: https://reportforge-api.vercel.app
Interactive Demo: https://reportforge-api.vercel.app/#try
Templates: https://reportforge-api.vercel.app/#templates
GitHub: https://github.com/AlberaMarc/reportforge-api
DocForge API (format conversion): https://docforge-api.vercel.app
The source code is MIT licensed.
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