Free DPI / PPI Changer — Set Image Resolution to 72, 150, 300 DPI

Print shops, magazine submissions and design software all care about DPI. Browsers and screens don't. PikDraw's DPI Changer edits the embedded resolution metadata of PNG and JPEG files — instantly, in your browser, with an optional resample mode that keeps the physical print size while raising the pixel count.

What is the DPI / PPI Changer — Set Image Resolution Metadata?

DPI Changer is a client-side tool that rewrites the pHYs chunk in PNG files and the JFIF density bytes in JPEG files. It supports two modes: metadata-only (changes the DPI tag without touching pixels) and resample (recomputes pixel count to maintain a physical size at the new DPI).

Key features

  • PNG pHYs chunk rewriting with correct CRC
  • JPEG JFIF density (APP0) rewriting, inserts JFIF marker if missing
  • Preset DPIs: 72, 96, 150, 300
  • Custom DPI up to 2400
  • Optional resample mode for physical-size preservation
  • Pixel data and ICC profile preserved in metadata-only mode
  • 100% client-side — no upload
  • Free, no signup, no watermark

How it works

For PNG, the tool walks the IDAT chunk list, strips any existing pHYs, builds a fresh 9-byte pHYs payload (X-PPM, Y-PPM, unit=1 metre) with a recomputed CRC32, and inserts it directly after IHDR. For JPEG, the tool either updates the existing APP0 (JFIF) marker's density bytes or inserts a new 16-byte APP0 segment immediately after SOI. In resample mode, the image is decoded, drawn onto a Canvas at the new pixel dimensions, and re-encoded with the same metadata rewrite applied to the output.

Why use this tool

Most online DPI tools require an upload, slow you down, and don't actually rewrite the resolution chunk — they just claim to. PikDraw's tool does the real metadata edit in your browser with correct CRC and JFIF placement, so the new DPI is honoured by every standards-compliant viewer and print driver. No upload, no signup, no waiting.

Common use cases

  • Fix 'image is only 72 DPI' rejections from a print shop
  • Prepare images for InDesign or Word documents that respect DPI
  • Convert web exports for use in a printed brochure
  • Match a specific physical size at a specific DPI for packaging
  • Submit photos to a stock library that requires 300 DPI
  • Bring scanned documents to a standard archival DPI
  • Match DPI across a multi-image print layout

How to use this tool

  1. Upload a PNG or JPEG — The tool edits the embedded resolution metadata of PNG (pHYs chunk) and JPEG (JFIF density). Other formats — WebP, AVIF, GIF — don't carry DPI in a standard way.
  2. Pick a target DPI — 72 for legacy web habit, 96 for modern Windows defaults, 150 for newspapers and posters, 300 for high-quality print. Custom values up to 2400 DPI are accepted.
  3. Decide whether to resample — Off (default): metadata only. Pixel count stays identical, only the print size changes. On: pixels are resampled so the image keeps its physical size at the new DPI — useful when matching print specs.
  4. Set reference DPI (resample only) — If you turn resampling on, tell the tool what DPI the original was authored at (default 72). The tool scales by target/reference — e.g. 72 → 300 quadruples pixel count.
  5. Download — Output is a PNG or JPEG with the new resolution embedded. Print drivers and DTP software (InDesign, Word, Pages) will now honour the new DPI.

Who should use this

Designers preparing print files. Photographers submitting to stock libraries with DPI requirements. Marketers exporting web banners for trade-show prints. Scanners archiving documents at a fixed DPI. Anyone receiving 'this file is low DPI' errors from a printer or DTP application.

How to get started

Upload your image, click 300 DPI, leave resample off, and download. The new file will be accepted by print drivers that previously rejected it.

Best practices

  • Metadata-only is enough for most print rejections
  • Resample only when physical size at target DPI is fixed
  • Don't expect a quality improvement from upsampling
  • Use PNG for line art / screenshots at high DPI
  • Use JPEG for photos at print DPI
  • Pair with our compress tool to keep print files under email-size limits
  • Verify by reopening in Photoshop / GIMP — both will show the new DPI

Pro tips

  • DPI alone never changes screen appearance — only print size.
  • For pure web work, DPI is irrelevant; browsers ignore it.
  • Print: 300 DPI for photos, 600+ DPI for line art and text.
  • If a printer rejects your file at '72 DPI', this tool is the fix — usually no resample needed.
  • Resample only when you must match a specific physical size at a specific DPI.

Expert insights

💡 Pro Tip: Screen vs print

If your destination is a screen, DPI doesn't matter. If your destination is paper, DPI controls how many inches your image will print to.

💡 Pro Tip: Metadata wins

For most '72 DPI rejected' errors, metadata-only is the right fix — instant, lossless, no quality change.

💡 Pro Tip: 300 = photo, 600 = line art

300 DPI is enough for any photo. Line art, text and barcodes look noticeably crisper at 600 DPI or higher.

Limitations to be aware of

  • PNG and JPEG only (no WebP, AVIF or GIF)
  • Metadata-only mode doesn't increase real resolution
  • Resample uses browser bicubic, not Photoshop bicubic-sharper
  • Does not modify EXIF resolution tags (separate from JFIF density)
  • DPI is ignored by browsers and screens
  • Single image at a time

Frequently asked questions

What's the difference between DPI and PPI?
PPI (Pixels Per Inch) describes pixel density on screens and in image files. DPI (Dots Per Inch) describes ink dot density of printers. Image-editing software, including this tool, treats them interchangeably — the metadata field is the same. The terminology distinction matters only when you're comparing a printer spec to an image spec.
Does changing DPI affect screen appearance?
No. Browsers, image viewers and screens render images pixel-for-pixel. A 1000×1000 image is 1000×1000 pixels regardless of whether the file says 72, 300 or 2400 DPI. DPI only matters for print, where it controls how many pixels go into each printed inch.
When do I need to resample?
Only when you must hit a specific physical size at a specific DPI. Example: a 1000×1000 image is 13.9 × 13.9 inches at 72 DPI. If you need it to print as 13.9 inches but at 300 DPI, you must resample to 4167×4167. Without resampling, 300 DPI would shrink the print to 3.3 inches.
Will resampling improve quality?
No. Upsampling invents pixels by interpolation — the image grows in dimensions but doesn't gain real detail. For genuine resolution boosts, use our upscale tool (which applies smarter algorithms) or re-shoot at higher resolution.
Does this work on WebP / AVIF / GIF?
Not currently. PNG (pHYs chunk) and JPEG (JFIF density) are the two formats with a well-defined DPI field. WebP can carry resolution metadata but most tools ignore it. AVIF and GIF have no equivalent. Convert to PNG first if your destination requires a non-72 DPI.
Is this safe for printer submissions?
Yes — this is the safest possible DPI change because it only writes the resolution chunk; pixel data and ICC profiles are preserved. Many printers reject 'low DPI' files even when the pixel count is large enough — this tool fixes that without altering the image itself.
Are my files uploaded?
No. PNG chunk insertion and JFIF header rewriting are done locally in the browser. No image data leaves your device — safe for client and unreleased work.
Why is my file size identical after the change?
Because in metadata-only mode you've added just a few bytes (the pHYs or JFIF density field). In resample mode the file size changes proportionally to the pixel-count change — 72 → 300 with resample multiplies the area by ~17×.

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