Forem: kabir daki

How I Reduced PDF File Size by 80% in the Browser — No Server Needed

kabir daki — Tue, 21 Apr 2026 23:24:36 +0000

When I started building PDFOnlineLovePDF, I faced one big challenge: how do you compress a PDF file entirely in the browser, without sending it to a server?

Most PDF tools upload your file to a remote server, process it, then send it back. That's slow, raises privacy concerns, and costs money to run at scale.

I wanted something different: 100% client-side PDF compression.

Here's exactly how I did it.

The Problem With Server-Side PDF Compression

Most online PDF tools work like this:

User uploads file → goes to your server
Server runs ghostscript or similar tool
Compressed file is sent back to the user

This works, but has real problems:

Privacy: Your files touch someone else's server
Speed: Upload + processing + download = slow
Cost: Server bandwidth and CPU are expensive
Scalability: 1000 users uploading 10MB files = infrastructure nightmare

I wanted to eliminate all of these problems.

The Solution: PDF.js + PDF-lib in the Browser

The key insight is that modern browsers are incredibly powerful. With the right libraries, you can parse, manipulate, and re-render PDF files entirely in JavaScript — no server required.

Here are the two libraries that made this possible:

1. PDF.js (by Mozilla)

PDF.js lets you read and render PDF files in the browser. It parses the PDF structure and gives you access to every page, image, font, and element.

import * as pdfjsLib from 'pdfjs-dist';

const loadPDF = async (file) => {
  const arrayBuffer = await file.arrayBuffer();
  const pdf = await pdfjsLib.getDocument({ data: arrayBuffer }).promise;
  return pdf;
};

2. PDF-lib

PDF-lib lets you create and modify PDF files entirely in JavaScript. You can add pages, embed images, compress content, and save the result as a new PDF.

import { PDFDocument } from 'pdf-lib';

const compressPDF = async (arrayBuffer) => {
  const pdfDoc = await PDFDocument.load(arrayBuffer);
  const compressedBytes = await pdfDoc.save({
    useObjectStreams: true, // This is key for compression
  });
  return compressedBytes;
};

The Compression Strategy

Simply re-saving a PDF with useObjectStreams: true gives you some compression, but not enough. The real gains come from re-rendering each page as a compressed image.

Here's the full strategy I used:

Step 1: Render Each Page to Canvas

const renderPageToCanvas = async (page, scale = 1.5) => {
  const viewport = page.getViewport({ scale });
  const canvas = document.createElement('canvas');
  canvas.width = viewport.width;
  canvas.height = viewport.height;

  const context = canvas.getContext('2d');
  await page.render({
    canvasContext: context,
    viewport,
  }).promise;

  return canvas;
};

Step 2: Convert Canvas to Compressed JPEG

const canvasToJpeg = (canvas, quality = 0.7) => {
  return new Promise((resolve) => {
    canvas.toBlob(
      (blob) => resolve(blob),
      'image/jpeg',
      quality // 0.7 = 70% quality, good balance
    );
  });
};

Step 3: Rebuild the PDF With Compressed Images

const rebuildPDF = async (originalArrayBuffer, quality = 0.7) => {
  const pdfjsLib = window['pdfjs-dist/build/pdf'];
  const loadingTask = pdfjsLib.getDocument({ data: originalArrayBuffer });
  const pdfDoc_original = await loadingTask.promise;

  const newPdfDoc = await PDFDocument.create();

  for (let i = 1; i <= pdfDoc_original.numPages; i++) {
    const page = await pdfDoc_original.getPage(i);
    const canvas = await renderPageToCanvas(page, 1.5);
    const jpegBlob = await canvasToJpeg(canvas, quality);
    const jpegArrayBuffer = await jpegBlob.arrayBuffer();

    const jpegImage = await newPdfDoc.embedJpg(jpegArrayBuffer);
    const { width, height } = jpegImage.scale(1);

    const newPage = newPdfDoc.addPage([width, height]);
    newPage.drawImage(jpegImage, {
      x: 0,
      y: 0,
      width,
      height,
    });
  }

  return await newPdfDoc.save();
};

The Results

Using this approach, here's what I observed across different PDF types:

PDF Type	Original Size	Compressed Size	Reduction
Scanned document (10 pages)	8.2 MB	1.4 MB	83%
Report with images (5 pages)	3.1 MB	0.7 MB	77%
Text-heavy document (20 pages)	1.8 MB	0.4 MB	78%
Presentation slides (15 pages)	12.4 MB	2.1 MB	83%

Average reduction: ~80% — entirely in the browser.

Quality vs Compression Tradeoff

The JPEG quality setting is the main lever you can pull:

// Higher quality = larger file, better text readability
const HIGH_QUALITY = 0.85;    // ~60% reduction
const MEDIUM_QUALITY = 0.7;   // ~75% reduction  
const LOW_QUALITY = 0.5;      // ~85% reduction

For my tool, I offer three preset levels so users can choose based on their needs:

High Quality — best for documents you'll print
Medium Quality — best for email attachments
Low Quality — best for web upload or WhatsApp sharing

Handling Large Files Without Freezing the UI

Processing large PDFs page by page can freeze the browser if you're not careful. The solution is to use Web Workers and update a progress bar as each page is processed.

// In your main thread
const worker = new Worker('/pdf-compress-worker.js');

worker.onmessage = (e) => {
  const { progress, result } = e.data;

  if (progress) {
    updateProgressBar(progress); // e.g. "Processing page 3 of 10"
  }

  if (result) {
    downloadFile(result);
  }
};

worker.postMessage({ file: arrayBuffer, quality: 0.7 });

// In pdf-compress-worker.js
self.onmessage = async (e) => {
  const { file, quality } = e.data;
  const totalPages = /* get from pdf */;

  for (let i = 0; i < totalPages; i++) {
    // process page i
    self.postMessage({ progress: `${i + 1} / ${totalPages}` });
  }

  self.postMessage({ result: compressedBytes });
};

Privacy as a Feature

One unexpected benefit of this approach: you can genuinely tell users their files never leave their device.

This turned out to be a real differentiator. Many users explicitly mentioned in feedback that they chose PDFOnlineLovePDF because they didn't want to upload sensitive documents (contracts, medical records, financial statements) to an unknown server.

The privacy benefit is not just marketing — it's a direct result of the technical architecture.

Limitations

This approach isn't perfect. Here are the tradeoffs:

1. Text becomes non-selectable
When you re-render pages as images, the text layer is lost. The output is a purely image-based PDF — you can't select or copy text from it.

2. File size depends on content complexity
Text-heavy PDFs compress more than image-heavy ones. A PDF that's already full of JPEG photos may not compress much.

3. Processing is CPU-intensive
On older or low-end devices, processing a 50-page PDF can take 10-20 seconds. The progress bar is essential for UX.

4. Very large files (100+ pages) are slow
For very large documents, a hybrid approach (client-side for preview, server-side for heavy processing) might be better.

What I Learned

Building this feature taught me several things:

The browser is more powerful than most developers assume. PDF manipulation, image compression, file download — all doable without a backend.
Privacy-first architecture is a real competitive advantage, especially for document tools.
Web Workers are underused. They make CPU-intensive tasks smooth and non-blocking.
UX matters more than perfect compression. Users care more about a fast, responsive experience than squeezing out the last few kilobytes.

Try It Yourself

The PDF compression tool is live at PDFOnlineLovePDF.com. It's completely free, no signup required.

If you're building something similar or have questions about the implementation, drop a comment below — happy to help!

If this was useful, consider following me here on DEV.to for more posts about building browser-based tools.

I built a free alternative to iLovePDF — here's what I learned

kabir daki — Thu, 16 Apr 2026 22:08:18 +0000

Everyone uses iLovePDF. I did too.

Until I realized: every file I uploaded was sitting on their servers.
Contracts. Invoices. ID scans.

That bothered me. So I built something different.

PDFOnlineLovePDF — 31 tools, zero uploads

Here's the core difference:

❌ iLovePDF → uploads your file to their server
✅ PDFOnlineLovePDF → processes everything in your browser

Your files never leave your device. Ever.

What it can do

Convert PDF to Word, Excel, PowerPoint
Compress PDF (up to 90% smaller)
Merge, split, rotate, crop
OCR — extract text from scanned PDFs
Translate PDF into 50+ languages
Sign, protect, watermark

All free. No signup. No limits.

The tech stack

Next.js 15 — fast, SEO-friendly
PDF.js + pdf-lib — browser-side processing
Tailwind CSS — clean UI

What's next

More tools
Better OCR accuracy
Mobile app (maybe)

Would love your feedback! 🙏
Search "PDFOnlineLovePDF" on Google or drop a comment below.

showdev #webdev #javascript #productivity #opensource

Show DEV: I built a free browser-based PDF toolkit with 31 tools tags: showdev, webdev, javascript, productivity ---

kabir daki — Wed, 15 Apr 2026 21:39:04 +0000

Hey DEV community! 👋

I just launched PDFOnlineLovePDF — a 100% free, browser-based PDF toolkit.

The problem

Every PDF tool I tried had at least one of these issues:

Expensive subscriptions
Full of ads
Uploads your files to remote servers (privacy risk)
Requires signup just to compress a file

So I built my own.

What it does

31 tools, all running 100% in your browser:

Convert PDF to Word, Excel, PowerPoint
Compress up to 90%
Merge, split, rotate
OCR (extract text from scanned PDFs)
Sign PDFs
Translate into 50+ languages (AI-powered)

How it works

Everything runs client-side using WebAssembly and modern browser APIs. Your files never leave your device. No server, no storage, no privacy risk.

Tech highlights

100% client-side processing
WebAssembly for performance
AI-powered translation
Zero dependencies on external servers

Try it

👉 pdfonlinelovepdf.com

Also live on Product Hunt if you want to show some support:
👉 Product Hunt page

Would love your feedback — what features would you add? 🙏

Best PDF Tools in 2026: I Tested 7 — Here's the Honest Truth

kabir daki — Mon, 13 Apr 2026 22:28:04 +0000

I spent a week testing the most popular PDF tools. Here's what I found — and why I ended up building my own.
Adobe Acrobat — Powerful, but $19.99/month for basic tasks is hard to justify.
iLovePDF — Clean UI, but hits limits fast and forces signup.
Smallpdf — Same story. 2 free tasks/day, then paywall.
PDF24 — Generous free tier, but no AI features.
Sejda — Good, but 3 tasks/hour limit.
PDFescape — Outdated UI, limited tools.
PDFOnlineLovePDF — 31 tools, no signup, no watermark, AI-powered. Built this one myself after getting blocked one too many times.
The gap nobody fills: unlimited + no signup + AI features together.
Try it free → pdfonlinelovepdf.com

I Tested Adobe, iLovePDF, and 5 Other PDF Tools — Then Built My Own (Free, No Limits)

kabir daki — Sat, 11 Apr 2026 15:54:29 +0000

Everyone has that moment.
You need to compress a PDF. You Google it. You click the first result. You upload your file. Then — "Sign up to download your file."
Or worse: "You've reached your free limit. Upgrade to Pro."
I got tired of it. So I tested the most popular PDF tools out there, and then I built my own. Here's what I found.

The Contenders
ToolFree LimitSignup RequiredAI FeaturesAdobe Acrobat2 tasks/dayYesYes (paid)iLovePDFLimited tasksYesNoSmallpdf2 tasks/dayYesNoPDF24UnlimitedNoNoSejda3 tasks/hourNoNoMy ToolUnlimitedNoYes

Adobe Acrobat — Powerful but Expensive
Adobe is the gold standard. The UI is polished, the features are deep, and the AI Assistant is genuinely useful. But the free tier is aggressively limited — 2 tasks per day — and the paid plan starts at $19.99/month.
For occasional users, it's overkill. For daily use without paying? Forget it.

iLovePDF — Great UI, Frustrating Limits
iLovePDF has a clean interface and covers most common tasks: merge, split, compress, convert. It's probably the most popular free option out there.
The problem? You hit the limit faster than you expect. And the "free" experience is designed to push you toward the paid plan. No AI features either.

Smallpdf — Same Story
Smallpdf is smooth and well-designed. But 2 tasks per day is basically nothing if you work with PDFs regularly. It also requires an account to do anything useful.

PDF24 — The Hidden Gem
PDF24 is genuinely generous. No signup, no hard limits, and it covers a wide range of tools. The UI feels a bit dated, but it works.
No AI features though.

So I Built My Own
After testing all of these, I noticed a gap: unlimited + no signup + AI features didn't exist in one place.
So I built [pdfonlinelovepdf] — a free PDF toolkit with 31 tools and AI features baked in. No account needed. No daily limits. No paywalls.
What it does that others don't:

✅ AI-powered PDF summarization
✅ Ask questions about your PDF (chat with PDF)
✅ All 31 tools completely free
✅ No signup, ever
✅ No file limits

The Honest Comparison
If you need deep editing and professional features → Adobe is worth paying for.
If you want a clean UI for occasional use → iLovePDF or Smallpdf work fine.
If you want unlimited, free, with AI → try what I built.

Final Thought
The PDF tool space is dominated by freemium products designed to frustrate you into paying. I wanted to see if it was possible to just... not do that.
So far, so good.
👉 [Try it free — no signup needed] https://pdfonlinelovepdf.com/

I built a free PDF toolkit with 31 AI tools — no signup, no limits

kabir daki — Mon, 06 Apr 2026 21:39:03 +0000

The Problem

Every PDF tool online either:

Costs money 💸
Requires registration 📧
Uploads your files to their servers 🔓

My Solution

I built PDFOnlineLovePDF — a 100% free, browser-based PDF toolkit.

What it does

31 tools including:

Convert: PDF to Word, Excel, PowerPoint, JPG
Edit: merge, split, compress up to 90%
AI-powered: translate into 50+ languages, summarize, OCR
Security: protect, unlock, redact

Why it's different

✅ No signup required

✅ Files never leave your browser

✅ 100% free, no limits

✅ Powered by AI

Try it

👉 https://pdfonlinelovepdf.com

Would love your feedback!