Delhi University’s Common Seat Allocation System (CSAS) registration asks for a stack of documents in one sitting — photograph, signature, Class 10 and 12 marksheets, category certificate if applicable, sometimes a PwBD or sports certificate — and each field enforces its own size ceiling. Get one wrong and the portal rejects the upload with little explanation, right when you’re trying to finish registration before a phase deadline closes.
Short version: CSAS(UG) sets a 50KB cap on the photograph, a cap of roughly 20-30KB on the signature, and two tiers for everything else — around 300KB for general supporting documents, up to 500KB for marksheets and category certificates. Compress PDF has a one-click DU CSAS preset targeting 300KB, which clears both document tiers with room to spare, plus a custom field if you’d rather use more of the 500KB allowance for a dense multi-page certificate.
What the CSAS portal actually asks for
These figures are published in DU’s CSAS(UG) admission bulletin on admission.uod.ac.in ahead of each registration cycle, and confirmed in the cycle’s document checklist covered by Careers360. Limits are set fresh for each academic year, so treat the numbers below as the pattern to expect, and check the current bulletin’s exact figures before you submit.
| Document | Format | Typical size cap | Notes |
|---|---|---|---|
| Photograph | JPG/JPEG | Up to 50KB | White/light background, passport style |
| Signature | JPG/JPEG | Around 20-30KB | Signed on white paper, scanned clean |
| Class 10 / Class 12 marksheet | JPG or PDF | Up to 500KB | Full mark sheet, not just the certificate |
| Category certificate (SC/ST/OBC-NCL/EWS) | JPG or PDF | Up to 500KB | Issued within the validity window the bulletin specifies |
| Other supporting documents (PwBD, sports, single girl child, etc.) | JPG or PDF | Around 300KB | Varies by document; check your specific field |
Two tiers, not one — that’s the detail most guides skip. A 300KB target clears every field on this list; a 500KB target gives marksheets and category certificates extra headroom if legibility is tight at 300KB.
Why uploads get rejected here
The scan is a photo taken at full phone-camera resolution. A marksheet or certificate shot at default camera settings routinely lands at 3-8MB for one page — DU wants under half a megabyte. That’s a resolution problem, not a formatting one, and it’s the single biggest reason first attempts fail.
The photo or signature misses its own, much tighter cap. People compress the certificate carefully, then upload a 200KB passport photo straight from a studio CD, forgetting the photo field caps out at 50KB — a fifth of what the document fields allow. Each field needs its own pass.
A multi-page certificate got combined into one file. Merge a two- or three-page category certificate to save an upload step, and you’ve also multiplied the content that has to fit inside the same 500KB ceiling — usually at the cost of readability.
The document is below the stated minimum. Less common, but real: an over-compressed file that’s technically tiny can get flagged as low-quality rather than accepted as “small enough.”
Rejections that have nothing to do with file size
Before you assume a flagged document is a compression problem, rule these out — no compression tool touches any of them:
- Your name doesn’t match across documents. CUET application, Class 12 marksheet, and category certificate need the same spelling for your name and your parents’ names, and the same date of birth. A dropped middle initial or a transliteration difference is enough to put an otherwise-fine upload on hold.
- The certificate has aged out. OBC-NCL and EWS certificates carry a validity window set by the issuing authority, and a certificate that was fine when you registered for CUET can be past that window by the time CSAS admission rounds run. Check the issue date against what the current bulletin asks for, not what worked earlier in the cycle.
- The format doesn’t match the field. Marksheet and certificate fields generally take JPG or PDF, but photo and signature fields are usually JPG only — a compressed PDF fails there no matter how small it is, because the field never wanted a PDF in the first place.
If a document gets flagged for one of these instead of size, CSAS registration typically opens a short correction window before each phase closes, letting you swap the flagged file without restarting the whole form — check your registration dashboard for it before assuming the seat is lost.
How to hit the exact number
- Scan or photograph each document once, in good light, without trying to max out quality. You don’t need 600 DPI for something getting compressed to 300-500KB regardless — a normal phone camera shot works fine and compresses more predictably than an ultra-high-res scan.
- Open Compress PDF and upload the document. Tap the DU CSAS preset for the 300KB target, which covers general supporting documents and gives marksheets and category certificates comfortable margin under their 500KB cap too. The result screen shows the exact output size next to your target, so you know immediately whether it landed under the limit instead of having to check file properties separately.
- For a marksheet or certificate that looks soft at 300KB, switch to the custom target field and type 450-500KB instead — still inside the bulletin’s limit, with more image quality preserved for dense text or a fine seal.
- Check the result at actual zoom before uploading. Look specifically at the registration number, the institution seal, and any small printed marks — these are what verification staff check first, and they’re the first details to blur if a target is pushed too low.
- Handle the photo and signature separately, with a passport-photo tool, not the PDF compressor. Those fields check pixel dimensions as well as file size — a cropping job, not a compression job.
The tool renders each page and re-encodes it as a JPEG at a quality level that searches for your target size, entirely inside your browser. Nothing about a marksheet or category certificate gets uploaded to a server in the process.
If a document won’t compress small enough to stay legible
This happens almost exclusively with one kind of file: a long, text-dense certificate, scanned at high contrast, where every word matters. Compression to a tight target means rasterizing the page into a JPEG, and there’s a real floor past which a text-heavy page turns blurry before it turns small enough — no setting gets around that, because it’s inherent to flattening text into an image.
Compress PDF already works around part of this automatically: for a tight target, it doesn’t just crush JPEG quality at one fixed resolution — it steps the render size down in stages and re-checks quality at each one, because a slightly smaller page at higher JPEG quality reads better for small print than a full-size page crushed to mush. You don’t have to manage that trade-off by hand; it’s what happens by default whenever you set a target size.
If you hit that floor on a document allowing up to 500KB, use the custom field and move the target up rather than fighting the preset down. If the document still won’t clear a cap without losing the registration number, rescanning at a slightly lower resolution to begin with usually helps more than re-compressing an already-oversized scan. If you’ve already been rejected once, My PDF Was Rejected for Wrong File Size covers the other common causes.
A practical note for CUET scorers heading into DU admission
If you sat CUET UG to get here, you’ve likely already hit a similar upload step on the CUET side, with its own three-way split between photo, signature, and certificate limits — see Compress PDF to 200KB for CUET Document Upload if you’re handling both registrations close together. And if your counselling path also runs through JoSAA for an engineering seat, that portal’s limits are looser but still exact — Compress PDF for JoSAA Counselling Uploads covers that one.
Start with the DU CSAS preset in Compress PDF, check the result at zoom, and confirm the current cycle’s exact figures on admission.uod.ac.in before you submit — bulletins get re-issued each year and the numbers have moved before.