How accurate are the GZIP size estimates?

GZIP sizes are exact — computed using the browser's native CompressionStream API. Brotli sizes are estimated at approximately 18% smaller than GZIP based on typical compression ratios for JSON payloads.

What does the cache hit rate setting do?

The cache hit rate models the percentage of requests served from cache without transferring the response payload. A 70% cache hit rate means only 30% of requests actually consume bandwidth.

How do I enable GZIP compression on my API server?

In nginx, add "gzip on; gzip_types application/json;" to your server block. In Express.js, use the compression npm package. Most CDNs enable GZIP and Brotli automatically for JSON content types.

Should I use GZIP or Brotli for my API?

Brotli achieves better compression (typically 15–25% smaller than GZIP) but requires more CPU. GZIP is the safe default. Brotli is worth enabling if your CDN supports it since the CDN handles the CPU cost.

Can I use this estimator for non-JSON API responses?

Yes — the estimator works with any text payload. Paste HTML, XML, CSV, or plain text responses and the GZIP compression will be computed accurately. The Brotli estimate is calibrated for JSON but is a reasonable approximation for other text formats.

REST API Response Size Estimator

Model any API endpoint's response payload and estimate compressed wire size across GZIP and Brotli at various client loads. Set request volume and cache hit rate to see daily and monthly bandwidth savings — making it easy to justify enabling Content-Encoding: gzip or br on your endpoints. All compression runs in your browser using the native CompressionStream API. No signup required.

Model any API endpoint's response payload and estimate compressed wire size across GZIP and Brotli. Set request volume and cache hit rate to see daily bandwidth savings at scale. All compression runs locally in your browser — your payload never leaves your device.

Sample Payload

Choose a preset or select 'Custom payload' to paste your own

API Response Payload2277 bytes raw

{
  "data": [
    {
      "id": 1,
      "name": "User 1",
      "email": "user1@example.com",
      "role": "admin",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 2,
      "name": "User 2",
      "email": "user2@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 3,
      "name": "User 3",
      "email": "user3@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 4,
      "name": "User 4",
      "email": "user4@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 5,
      "name": "User 5",
      "email": "user5@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 6,
      "name": "User 6",
      "email": "user6@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 7,
      "name": "User 7",
      "email": "user7@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 8,
      "name": "User 8",
      "email": "user8@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 9,
      "name": "User 9",
      "email": "user9@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    },
    {
      "id": 10,
      "name": "User 10",
      "email": "user10@example.com",
      "role": "member",
      "active": true,
      "createdAt": "2024-01-15T10:00:00Z",
      "lastLogin": "2024-05-28T08:30:00Z"
    }
  ],
  "meta": {
    "total": 10,
    "page": 1,
    "perPage": 10
  }
}

Scale Settings

Request Volume

Total API calls per day

Cache Hit Rate

% of requests served from cache

Why Use Our REST API Response Size Estimator?

Instant REST API Response Size Estimation

Estimate REST API response sizes instantly in your browser — no server upload, no external libraries. Our rest api response size estimator uses the browser's native CompressionStream API for exact GZIP sizes and estimates Brotli savings.

Secure REST API Response Size Estimator Online

Your API response payload never leaves your device when you use this rest api response size estimator. 100% client-side processing means complete privacy — no cloud storage, no server logs, no API payload exposure.

REST API Response Size Estimator — No Installation

Estimate REST API response sizes directly in your browser with no software downloads, no npm packages, and no account required. This free rest api response size estimator works on any modern browser.

Bandwidth at Scale with Cache Hit Rate

Set request volume (1K to 100M/day) and cache hit rate to see daily and monthly bandwidth projections for uncompressed, GZIP, and Brotli responses — making it easy to justify enabling compression on your endpoints.

Common Use Cases for REST API Response Size Estimator

API Compression ROI Justification

Use the rest api response size estimator to quantify bandwidth savings before enabling GZIP or Brotli on your API server. Paste a typical endpoint response and show stakeholders the exact GB/day saved at your request volume.

CDN & Egress Cost Planning

Estimate monthly egress costs before and after enabling compression using the rest api response size estimator. At $0.08/GB egress, saving 500 GB/month translates to $40/month — the estimator makes this calculation instant.

API Performance Optimization

Use the rest api response size estimator to identify which endpoints have the highest compression opportunity. Large JSON responses with repeated keys and string values compress most aggressively — prioritize those first.

Mobile API Payload Optimization

Estimate how much data mobile users save per request using the rest api response size estimator. At 100K daily mobile users, reducing a 50 KB response to 15 KB with GZIP saves 3.5 GB of mobile data per day.

API Design & Payload Modeling

Use the rest api response size estimator during API design to compare different response shapes. Paste two candidate response structures and compare their compressed wire sizes to choose the more efficient design.

Cache Strategy Planning

Set the cache hit rate in the rest api response size estimator to model the effective bandwidth impact of your caching strategy. See how a 70% cache hit rate reduces effective bandwidth by 70% before compression is even applied.

Understanding REST API Response Compression

What is REST API Response Compression?

REST API response compression is the process of reducing the byte size of HTTP response bodies using lossless compression algorithms before transmission. Our rest api response size estimator models this process for any JSON payload — showing exact GZIPsizes (computed via the browser's native CompressionStream API) and estimated Brotli sizes. JSON API responses typically achieve 60–85% compression with GZIP and 65–90% with Brotli, because JSON contains many repeated keys, whitespace, and predictable patterns that compress extremely well. The estimator also models bandwidth at scale with configurable request volume and cache hit rate.

How Our REST API Response Size Estimator Works

1Paste your API response: Enter any JSON response payload — user lists, product catalogs, analytics events, or any endpoint response. The rest api response size estimator accepts any valid JSON structure. Use the preset samples to get started instantly.
2Set scale parameters: Choose your request volume (1K to 100M/day) and cache hit rate (0–90%). The estimator calculates effective requests (total minus cached) and projects daily and monthly bandwidth for each compression format.
3Review the estimation report: See per-response sizes for raw JSON, minified JSON, GZIP, and Brotli — plus daily and monthly bandwidth projections at your configured scale. A recommendation panel suggests the optimal compression strategy for your payload.

What the Estimator Calculates

Raw JSON size:The byte count of your formatted JSON payload as entered, measured using the browser's TextEncoder API for accurate UTF-8 byte counting.
Minified JSON size: The byte count after removing all whitespace via JSON.stringify — this is what a well-configured API server actually sends before compression.
GZIP size (exact):The actual compressed byte count computed using the browser's native CompressionStream API — not an estimate, but the real GZIP output size.
Brotli size (estimated): Estimated at approximately 18% smaller than GZIP, based on typical Brotli compression ratios for JSON payloads at quality level 6.

How to Enable Compression on Your API Server

In nginx, add gzip on; gzip_types application/json; to your server block. For Brotli, install the ngx_brotli module and add brotli on; brotli_types application/json;. In Express.js, use the compression npm package. In Next.js, compression is enabled by default in production. MostCDNs (Cloudflare, Fastly, AWS CloudFront) enable GZIP and Brotli automatically for JSON content types. Use the rest api response size estimator to quantify the savings before and after enabling compression.

Related Tools

JSON Key Shortener

Shorten verbose JSON keys to single letters or abbreviated forms — shows size reduction and provides a downloadable key mapping file for restoration. Free online JSON key shortener.

JSON vs MessagePack Size Comparison

Compare JSON byte size vs MessagePack encoding for any payload — shows exact savings, type-by-type breakdown, and MessagePack hex preview. Free online JSON vs MessagePack comparison.

String Decompressor (GZIP/LZ)

Decompress GZIP+Base64, DEFLATE+Base64, and LZ-String compressed payloads back to readable text — supports all three LZ-String variants. Free online string decompressor.

ZIP File Extractor

Extract files from any ZIP archive client-side — browse contents, preview text files, download individual files or all at once. Free online ZIP extractor, no signup required.

Frequently Asked Questions About REST API Response Size Estimator

The rest api response size estimator models any API endpoint's response payload and estimates compressed wire size across GZIP and Brotli at various client loads. It shows per-response sizes and daily/monthly bandwidth projections. All compression runs locally in your browser — your payload never leaves your device.

GZIP sizes are exact, not estimated. The rest api response size estimator uses the browser's native CompressionStream API to apply real GZIP compression to your minified JSON payload. The compressed size shown is the actual byte count of the GZIP output.

Brotli sizes are estimated at approximately 18% smaller than GZIP, based on typical Brotli compression ratios for JSON payloads at quality level 6. Actual Brotli savings depend on the compression level (1–11) and content characteristics. Higher Brotli levels achieve better compression but require more CPU.

Absolutely. The rest api response size estimator processes everything locally in your browser. Your API response payload is never uploaded to any server, never stored, and never leaves your device — completely safe for responses containing sensitive data.

Yes — 100% free, forever. No signup, no account, no premium tier, no payload size limits, and no ads interrupting your workflow.

The cache hit rate models the percentage of requests served from a CDN or server cache without hitting your origin. A 70% cache hit rate means only 30% of requests actually transfer the response payload. The estimator multiplies total requests by (1 - cache hit rate) to calculate effective bandwidth.

JSON API responses with many repeated keys, string values, and nested objects compress most aggressively — typically 70–85% with GZIP. Responses with many unique strings, UUIDs, or base64-encoded data compress less. The rest api response size estimator shows the exact compression ratio for your specific payload.

In nginx, add "gzip on; gzip_types application/json;" to your server block. In Express.js, use the compression npm package. In Next.js, compression is enabled by default in production. Most CDNs (Cloudflare, Fastly, CloudFront) enable GZIP and Brotli automatically for JSON content types.

Brotli achieves better compression than GZIP (typically 15–25% smaller) but requires more CPU for encoding. For APIs, GZIP is the safe default — it is supported by all HTTP clients. Brotli is worth enabling if your CDN supports it (Cloudflare, Fastly, and most modern CDNs do) since the CDN handles the CPU cost.