Free Browser Tool · No Signup

Free Photo Compressor Online

Compress, resize, crop, and download JPG, PNG, JPEG, and WEBP photos directly in your browser. Your image is processed locally on your device.

Photo Compressor

Upload a photo, choose target size, resize or crop, then download.

← Back Home

📷

Click to upload photo

JPG, JPEG, PNG, WEBP supported. Drag and drop also works.

Target Size KB

Example: 50, 100, 200, 500 KB. JPG is best for exact compression.

Output Format

WEBP is smaller, JPG is most compatible, PNG keeps transparency.

Size Unit

Width

Height

DPI for CM / MM / INCH

Physical units are converted to pixels using DPI. Example: 1 inch at 300 DPI = 300 px.

Without crop, the image keeps its original ratio. With crop, it matches your selected width and height ratio.

Enable cropping

Download Photo

How to Use

Upload your photo.
Choose target file size in KB.
Select JPG, WEBP, or PNG.
Resize or crop if needed.
Download the compressed image.

Best Settings

Use JPG for documents and general photos.
Use WEBP for smaller website images.
Use PNG only when transparency is needed.
Use crop for exact width and height.

Why Shader7?

No signup required.
Works on phone and PC.
Supports resizing in PX, CM, MM, and inch.
Simple tool made for fast daily use.

About This Free Photo Compressor

Shader7 Photo Compressor helps you reduce image file size for online forms, websites, documents, email attachments, and social media uploads. You can compress JPG, PNG, JPEG, and WEBP files, resize dimensions, crop to a selected ratio, and download the final photo instantly.

The Science of Digital Image Compression

Reducing an image's file size requires balancing the file's storage size with its visual fidelity. There are two primary categories of compression:

Lossy Compression: Used predominantly by JPEG and WEBP, this method analyzes pixel grids and discards visual details that the human eye is less sensitive to, such as minute color gradients. This allows for extremely large reductions in file size (often up to 90%) with minimal visible loss in quality. It is the ideal format for standard digital photos, social sharing, and fast-loading web images.

Lossless Compression: Employed by PNG, this format preserves every single pixel's color information exactly. Because no data is discarded, file sizes remain relatively large. It is highly optimized for vector layouts, crisp line art, digital text, and graphics requiring transparent backgrounds (alpha channels).

Physical-to-Pixel Conversion & DPI Calculator Math

When submitting photos for official documents, applications, or print media, dimensions are often specified in physical lengths (like millimeters, centimeters, or inches) rather than digital pixels. To translate these physical dimensions into digital pixels, you must use a density factor known as DPI (Dots Per Inch) or PPI (Pixels Per Inch).

To calculate the exact pixel width or height, use the following mathematical equations:

Pixels = Width (in inches) × DPI

If your measurements are in centimeters or millimeters, you must first convert the length to inches (1 inch is exactly 2.54 centimeters, or 25.4 millimeters):

Pixels = (Width in millimeters ÷ 25.4) × DPI
Pixels = (Width in centimeters ÷ 2.54) × DPI

For example, if you require a 5 cm × 5 cm photo at 300 DPI:
Width: (5 ÷ 2.54) × 300 ≈ 591 pixels.
This built-in converter performs this math automatically when you switch units from PX to CM, MM, or Inch!

Related Expert Guides & Resources

Enhance your image editing knowledge and digital security with our comprehensive expert articles:

Online Image Compression Guide

A deep-dive article into lossless vs lossy formats, DPI calculations, and how to compress photos for school or job portals.

Read Expert Guide →

Online Web Tool Security & Privacy

Learn how client-side JavaScript execution keeps your data 100% secure by processing images local in your system browser.

Read Expert Guide →

DIY Passport Photography Setup

Setup a perfect DIY passport photo environment using natural window light to avoid shadow and comply with guidelines.

Read Expert Guide →

Frequently Asked Questions

How does the browser-based photo compression work?

The photo compressor runs entirely inside your web browser using HTML5 Canvas APIs. When you select an image, the browser loads it locally into memory, applies the requested width/height adjustments, and renders it onto a canvas. It then compresses the canvas to your target size or quality without ever uploading the file to a remote server.

What is the difference between lossy and lossless compression?

Lossy compression (used in JPG and WEBP) decreases file size by permanently discarding less noticeable visual data, which is highly efficient for general photos. Lossless compression (used in PNG) retains all pixel-by-pixel information exactly, resulting in larger file sizes but keeping crisp transparency and sharp edges for graphic logos.

How do I calculate pixel dimensions from physical sizes like CM or Inches?

To convert physical units to pixels, you must specify a target resolution measured in DPI (Dots Per Inch). The mathematical equations are: Pixels = (Physical Size in Inches) * DPI, or Pixels = (Physical Size in Millimeters) * DPI / 25.4. For example, a 5cm x 5cm photo at 300 DPI converts to 591px x 591px.

Can I lock or unlock the aspect ratio during crop or resize?

Yes. By default, the tool maintains your photo's original proportions to prevent stretching. If you toggle cropping, you can define custom dimensions (like a square 1:1 or standard document ratios) and resize the bounding box freely before compression.

Is there a limit to the image file size I can upload?

Because all operations are performed on your local device, there are no strict upload limits. However, extremely large files (e.g., above 30MB or 8000px dimensions) can consume substantial system RAM on mobile devices during rendering.

Is my uploaded photo stored or shared?

No. Privacy is a core feature of Shader7. Since the tool operates 100% client-side, your photos remain secure on your own device. No data is sent to external servers, protecting your privacy completely.

The Mathematics of Lossy DCT & Lossless Huffman Compression

Digital images require immense storage space if saved as raw pixels. To optimize images for web performance, modern compressors use either lossy algorithms (such as JPEG/WebP) or lossless algorithms (such as PNG). Our Photo Compressor operates directly inside your browser using canvas rendering pipelines, allowing you to compress images with zero server-side exposure.

The mathematical principles governing these compression methods are:

Lossy Discrete Cosine Transform (DCT): Used in JPEG compression to convert spatial 8x8 pixel grids into frequency domains. Low-frequency values are preserved, while high-frequency details (which human eyes barely detect) are divided by values in a Quantization Matrix and discarded: C_(u,v) = round( F_(u,v) / Q_(u,v) ).
Lossless Huffman & LZW Coding: Used in PNG compression to scan repetitive patterns of data and index them in a dynamic dictionary, reducing file size with absolutely zero loss in quality.

Step-by-Step Image Optimization Guidelines

Select the Right Format: Use **PNG** for screenshots, diagrams, text layouts, and images containing transparency; use **JPEG** or **WebP** for real-world photography and complex colorful scenes.
Calibrate Compression Ratio: Set your target quality percentage between 70% and 85%. This represents the sweet spot, yielding up to a 90% reduction in file size while retaining excellent visual fidelity.
Resize to Target Boundaries: Lowering spatial resolution (width and height) is the most effective way to reduce file sizes. Our tool allows custom dimensions in pixels, centimeters, and inches.
Preserve Color Profiles: The compressor automatically retains standard sRGB profiles to ensure consistent color rendering across different mobile and desktop displays.

Understanding Compression Metrics

When compressing files, the compression ratio is calculated as: CR = Original Size / Compressed Size. A compression ratio of 10:1 indicates that the optimized file is only 10% of the original size. The tool displays this metric in real time so you can audit optimization thresholds before downloading.

Photo Compressor Frequently Asked Questions (FAQ)

Q: What is the difference between JPEG and WebP?
A: WebP is a modern web image format developed by Google that offers both lossy and lossless compression. WebP files are typically 25% to 30% smaller than JPEGs at equivalent quality settings, and they support transparent alpha channels.

Q: Does compressing an image reduce its print quality?
A: Yes, if the quality index is set too low (under 60%) or if the pixel dimensions are downscaled. For print, keep pixel dimensions intact and maintain quality above 85% at a minimum resolution of 300 DPI.

Q: Are my uploaded photos safe?
A: Absolutely. Our compressor is built using Web Assembly and HTML5 canvas APIs that process the image bytes directly within your local browser memory. No data is transmitted to external servers, ensuring complete privacy.