The initial flow worked on small datasets, but once the API returned larger responses, the redirect started failing with errors such as:

HTTP ERROR 431 (Request Header Fields Too Large)

or occasionally:

HTTP ERROR 414 (URI Too Long)

⚠️ Root Cause

The application used a pattern like:

const encoded = encodeURIComponent(JSON.stringify(data));
window.location.href = `/result?data=${encoded}`;

This meant the entire API response (often several kilobytes of JSON) was being attached to the URL as a query parameter.

Why this fails

• Most browsers and proxies enforce strict limits on URL length (usually 8–16 KB total, including headers).
• Exceeding that limit triggers a 431 or 414 error, depending on where it fails (proxy vs browser).
• Even before failure, such URLs break analytics, browser history, and caching.

💡 Solution: Store Data Locally, Pass Only a Key

Instead of serializing the full JSON in the URL, the client now saves it in sessionStorage and only includes a short identifier in the query.

Example Implementation

// 1️⃣ Save data locally
const key = `result_${Date.now()}`;
sessionStorage.setItem(key, JSON.stringify(data));

// 2️⃣ Redirect using only the key
window.location.href = `/result?key=${key}`;

Then, on the result page:

// 3️⃣ Read data on load
const params = new URLSearchParams(window.location.search);
const key = params.get("key");

if (key) {
const stored = sessionStorage.getItem(key);
if (stored) {
const parsed = JSON.parse(stored);
renderResults(parsed);
}
}

✅ Benefits

• URL length reduced from ~10 KB → <100 bytes
• No more 431 or 414 errors
• No sensitive data in logs or browser history
• Smooth navigation across repeated searches or actions
• Works consistently in dev, staging, and production environments

🧠 Key Learnings

LessonDescription

Never put large JSON in query strings

Keep URLs lightweight — identifiers only.

Use sessionStorage or localStorage

Great for short-lived client-side data between pages.

Mind proxy limits

Many CDNs, firewalls, and browsers cap header + URL size to ~8 KB.

Clean up after use

Remove old session keys to prevent buildup.

Avoid leaking data

URLs are logged, cached, and shared — never store sensitive info there.

📘 Best Practice Pattern

🧩 Store large payloads locally or on the backend,
🔑 Send only a small key or token in the URL,
💾 Retrieve and render data after navigation,
🚫 Keep URLs under 2 KB total for safety.

✅ Outcome

After refactoring:

• Navigation became instant and reliable.
• The app no longer triggered 431/414 errors.
• The approach now scales regardless of API payload size.