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CORS Proxy

The PondPilot CORS Proxy is a transparent proxy service that enables browser-based applications to access remote files and databases that don’t have CORS headers configured. All requests are proxied without logging, caching, or modification—your data remains private.

What is CORS?

Section titled “What is CORS?”

Cross-Origin Resource Sharing (CORS) is a browser security mechanism that prevents web pages from making requests to different domains unless the server explicitly allows it. When you try to load a file from https://data.example.com in a web app running at https://app.pondpilot.io, your browser blocks the request unless data.example.com sends proper CORS headers.

┌─────────────────┐         ┌─────────────────┐
│   Your Browser  │ ──────▶ │  Remote Server  │
│  (PondPilot)    │ ◀────── │  (no CORS)      │
└─────────────────┘   ❌    └─────────────────┘
                    Blocked by browser security

Many public data sources—S3 buckets, CloudFront distributions, government data portals—don’t include CORS headers, making them inaccessible from browser-based tools like PondPilot.

How the CORS Proxy Helps

Section titled “How the CORS Proxy Helps”

The CORS Proxy acts as an intermediary that:

  1. Receives your request from PondPilot
  2. Fetches the data from the original source
  3. Adds proper CORS headers to the response
  4. Returns the data to your browser
┌─────────────────┐         ┌─────────────────┐         ┌─────────────────┐
│   Your Browser  │ ──────▶ │   CORS Proxy    │ ──────▶ │  Remote Server  │
│  (PondPilot)    │ ◀────── │  (adds headers) │ ◀────── │  (no CORS)      │
└─────────────────┘    ✓    └─────────────────┘    ✓    └─────────────────┘

When You Need the CORS Proxy

Section titled “When You Need the CORS Proxy”

Use the CORS Proxy when accessing:

  • Remote Parquet/CSV files on S3, CloudFront, or other CDNs without CORS
  • Remote DuckDB databases for read-only analytics
  • Public data portals (data.gov, data.gouv.fr, etc.)
  • GitHub raw files and releases
  • Any HTTPS resource blocked by browser CORS policies

PondPilot automatically uses the CORS Proxy when loading remote files that would otherwise fail.

Privacy Guarantees

Section titled “Privacy Guarantees”

The CORS Proxy is designed with privacy as a core principle:

  • No Logging - Request URLs and data are never logged or retained
  • No Caching - Data passes through without storage
  • No Modification - Responses are streamed unaltered
  • No Tracking - No cookies, analytics, or user identification
  • HTTPS Only - All traffic is encrypted in transit

Usage Options

Section titled “Usage Options”

Official Hosted Service

Section titled “Official Hosted Service”

The official proxy is available at https://cors-proxy.pondpilot.io:

https://cors-proxy.pondpilot.io/proxy?url=https://example.com/data.parquet

This service is free, globally distributed via Cloudflare’s edge network, and automatically used by PondPilot when needed.

Self-Hosted

Section titled “Self-Hosted”

For maximum privacy or enterprise requirements, you can run your own proxy:

Terminal window
docker run -p 3000:3000 ghcr.io/pondpilot/cors-proxy

See the Self-Hosting Guide for deployment options.

Section titled “Quick Links”

Usage Guide

Learn how to use the CORS Proxy with PondPilot and other tools.

View usage →

Self-Hosting

Deploy your own CORS Proxy with Docker or Cloudflare Workers.

Self-host →

Security

Security features, SSRF protection, and configuration options.

Learn more →