If this is your first time applying to a competitive exam, the photo and signature specification section of the notification can read like a foreign language: "200×230 pixels," "20-50KB," "200 DPI, JPG format." None of this is explained, and most guides assume you already know what these terms mean. This article doesn't cover any exam's specific numbers — it explains what the units themselves actually mean, so the specification on any exam's notification makes sense the moment you read it.
Pixels: The Actual Size of the Image
A digital photo is made of a grid of tiny colored dots called pixels. When a spec says "200×230 pixels," it means the image should be exactly 200 dots wide and 230 dots tall — not 200 dots on your screen at some zoom level, but 200 actual pixels in the file itself, however large or small that appears when displayed. This is why a photo can look perfectly clear on your phone screen but still be "300×345 pixels" or some other size that doesn't match — the pixel count is a property of the file, not of how big or small it looks when you view it.
Resizing to an exact pixel count means the tool redraws your original photo onto a new canvas of exactly that many pixels — 200 wide, 230 tall, or whatever the spec calls for. This is different from just "shrinking" or "zooming" — a proper resize recalculates every pixel to fit the new grid, which is why using a purpose-built resize tool gives a cleaner result than dragging the corner of an image in a basic viewer.
DPI: Mostly a Legacy Term for Digital Uploads
DPI stands for "dots per inch," and it originally described print resolution — how many ink dots a printer places in one inch of paper. For a printed photo, higher DPI means finer, more detailed print quality. For a digital file being uploaded to a website, DPI is largely a leftover concept: what actually matters for an on-screen upload is the pixel count (covered above), not the DPI value embedded in the file's metadata. Many exam specifications still list "200 DPI" as a requirement — largely because official specifications were originally written with printing and physical documents in mind — but as long as your pixel dimensions and file size match what's asked, the DPI metadata value rarely causes a rejection on its own for a digital upload.
KB: The Actual Weight of the File
KB (kilobytes) measures how much storage space the image file takes up — essentially, how much data was needed to store the image. A larger pixel count generally means more data and thus a larger KB size, but the relationship isn't fixed, because compression changes how efficiently that pixel data is packed into the file. This is the key idea behind hitting a specific KB target: the same 200×230 pixel photo can be saved at very different file sizes depending on how much compression is applied — a lightly compressed version might be 80KB, while a heavily compressed version of the exact same pixel dimensions might be 20KB, with a corresponding loss of fine detail.
This is why exam specifications give both a minimum and maximum KB, not just a maximum: too little compression makes the file too large to fit the upload limit, while too much compression can degrade the image so much that a face or signature becomes hard to make out clearly — which is its own problem even if the file technically satisfies the KB number.
Putting the Three Together: Reading an Actual Specification
A typical exam specification — say, "200×230 pixels, 20-50KB, JPG, 200 DPI" — breaks down like this: the image must be exactly 200 pixels wide and 230 pixels tall (the actual grid of dots that makes up the photo), the resulting file must weigh between 20KB and 50KB (controlled by how much compression is applied), it must be saved in JPG format (see our format guide for why JPG specifically), and the DPI metadata value should read 200 (a legacy field that matters far less than the pixel count and KB size for a digital upload).
A tool like the image resize tool handles the pixel-dimension part, while a KB-targeting tool like compress to a specific KB handles the file-size part — and for exam-specific pages, both are usually combined into a single tool that loads the correct numbers automatically, so you don't have to calculate any of this by hand.
Why Getting All Three Right Matters Together
A file can satisfy one of these three requirements without satisfying the others — the pixel dimensions can be exactly right while the KB size is way off, or the format can be correct while the dimensions are stretched out of proportion. Portal validation checks all three independently, so a photo that's "close enough" on two out of three still fails. This is the core reason exam-specific resize tools exist at all: rather than manually guessing at compression settings until a file happens to land in the right KB range, a tool that knows the target pixel dimensions and KB range can hit all three requirements — dimensions, size, and format — in one pass.