Quick answer
Set the target to 100 KB. The tool repacks the PDF first without changing it; if that is not enough it redraws the pages at 150, 110, 96, 72, 60 and 48 dpi and stops at the first step that fits. At 96 dpi an A4 page has 0.89 million pixels, so 100 KB allows about 0.92 bits per pixel for one page, and extra pages share the same limit.
| Resolution | A4 page in pixels | Bits per pixel available |
|---|---|---|
| 150 dpi | 1241 × 1754 | 0.38 |
| 110 dpi | 910 × 1286 | 0.70 |
| 96 dpi | 794 × 1122 | 0.92 |
| 72 dpi | 595 × 842 | 1.64 |
| 60 dpi | 496 × 701 | 2.36 |
| 48 dpi | 397 × 561 | 3.68 |
These figures are computed with the same formulas as the Compress PDF to 100KB above. Change the inputs in the tool to see your own result.
Compress PDF to 100KB shrinks a PDF until it fits under 100 kilobytes, the limit many government, exam, scholarship and bank upload forms set for supporting documents. The tool first repacks the file without touching its content, which is often enough for a typed document. If the file is still too big, it lowers the quality of the page images step by step, stopping at the first setting that fits so the result stays as readable as possible. It runs in your browser, so your certificates and ID copies are never uploaded.
Made for everyone. Typical uses:
A one-page scanned certificate of 640 KB usually needs the image steps and lands near 60 to 95 KB at around 72 to 96 dpi, still readable on screen. A typed one-page letter saved from a word processor is often already under 100 KB, and a lossless repack alone may shave it further.
A 100 KB budget is tight. One or two pages of a scan usually fit, but a ten-page scan cannot be made that small without becoming hard to read, so split it and upload the parts if the form allows. Once the images are lowered the pages are pictures, so the text can no longer be selected or searched. Password-protected files must be unlocked first.
Accuracy: Files are processed with established open-source libraries and tested with real PDFs. Open the result and check it before you send or publish it.
Expert Tip
Scan at 150 dpi in black and white or grayscale instead of colour photos from your phone, and crop the edges before you scan. A clean, cropped, black and white scan starts several times smaller, so far less quality has to be removed.
A limit of 100 kilobytes comes from the way many older and public-sector upload systems are built. Each applicant may upload several documents, thousands of people apply on the same day, and a small cap keeps storage costs and page load times down. You meet it on exam registrations, scholarship portals, tax and bank sites, and visa or admission forms. The limit is rarely negotiable, so the file has to change instead.
It helps to know how little 100 KB is. A plain typed page saved from a word processor is often 20 to 80 KB, so it already fits. A scanned page is a picture, and a picture at reading quality takes far more room. That gap is why a one-page certificate can be 600 KB while the same text typed out is 40 KB.
The Compress PDF to 100KB page works in an order that protects quality. It first repacks the file without changing what you see, which can remove wasted data. If that is not enough, it rebuilds the pages as images at a series of resolutions, starting around 150 dots per inch and stepping down through 110, 96, 72, 60 and 48. It stops at the first step where the file is under your limit, so you get the best-looking result that fits rather than the smallest possible one.
Because the later steps turn each page into a picture, the text is no longer selectable. For an upload that a person will read on a screen, that rarely matters. For a document that must be searched or copied, keep the original as well.
Plan around the number of pages and how they were made. As a guide, expect the following.
The biggest gains come before the tool is involved. Scan in grayscale or black and white rather than colour, at 150 dpi rather than 600. Crop away the dark borders around the page, because they are expensive to store and carry no information. Flatten the lighting so the paper is a clean white; a grey background is data too.
If you start from a phone photo, turn it into a PDF with JPG to PDF after cropping and lowering its size with the Image Resizer, then compress the PDF. For a bundle of documents, Split PDF lets you upload each part within its own limit.
Open the compressed file and read the smallest print: dates, numbers and names are what portals and reviewers check. If any of them is hard to read, the quality is too low for the purpose, and a different approach is better than submitting a file that gets rejected later. When the limit leaves no choice, the more specific 200 KB version is worth trying if the portal allows a bit more room.
Nothing you choose here leaves your device. The compression runs inside the browser tab, which matters for identity documents and certificates.
How much a PDF can shrink, why scans are the problem, how many pages fit under each size limit, and how our tool reaches a target without ruining the text.
Pick the right method for scans, slides, photos and text documents, hit email and upload limits, and stop big PDFs at the source with better scan and export settings.
Explore more in PDF Tools, read the guides and articles, or see how we test our tools.
Reduce PDF file size to a target you set, or with lossless optimizing or a smaller image-based copy.
Best for getting a PDF under the size cap of a job, visa, school or government upload form
Extract specific pages from a PDF file.
Best for sending only the relevant pages of a long report or contract
Combine multiple PDF files into one.
Best for combining a cover letter, CV and certificates into one application PDF
Shrink a PDF to under 200 KB for application portals.
Best for attaching a CV and a certificate to a job application form
Convert PDF pages to JPG images.
Best for extracting a single page from a PDF as an image to share or embed
Get an image under 100 KB while keeping it sharp.
Best for uploading photos to a job, college or government form with a 100 KB limit