Bulk image resizer

Plan a batch before adding every file

A batch is most useful when its files share a delivery requirement, not necessarily a composition. Group photographs by the rule they must meet: a maximum side, a square catalog canvas or an attachment ceiling. Keep unrelated tasks in separate runs. One set of crop coordinates can fit the first product and cut the next one in half. A shared fit box is more forgiving because each source keeps its own ratio.

Make a pilot export, review the smallest and most detailed images, then process the collection. During a run, keep the tab open and inspect the progress and success counts. Download finished images individually or collect successful outputs in ZIP. If one file fails, review its own format, dimensions and error rather than discarding the whole batch. Cancel clears the active work; changing settings starts a fresh configuration for the next run.

Start with the destination, not a random number

An image is ready when it meets the place where it will be used. A page may ask for a maximum width; an upload form may enforce a byte ceiling; a layout may need an exact rectangle. Those requirements are related, but they are not interchangeable. Write down the destination’s actual instructions before you change the source. “Make it smaller” is a direction. “Keep the complete photo within 1600 × 1600 and below 500000 bytes” is a testable result.

Separate the non-negotiable rules from your preferences. If every product must stay visible, cropping is not an acceptable shortcut. If a form requires PNG, switching to JPEG is not a solution. If a fixed canvas is mandatory, fit mode alone may leave you with the wrong dimensions. The best settings are the ones that satisfy the hard rules while keeping useful detail.

Batch resizing should respect each original

One batch configuration does not imply one result shape. With a 1600 × 1600 fit box, a 4000 × 3000 landscape becomes 1600 × 1200, while a 3000 × 4000 portrait becomes 1200 × 1600. Each image keeps its own ratio. Use a padding canvas when outer dimensions need to match. Avoid applying one crop rectangle to unrelated compositions without checking each subject.

Process a small representative set first: one landscape, one portrait, one transparent graphic and your smallest source. Inspect those results before admitting the whole collection. Jobs run sequentially, and an unsupported file need not prevent supported files from finishing. The archive contains successful results, so compare the success count with the files you expected to receive.

Choose the format for the image you actually have

Photographs, transparent logos and screenshots stress an encoder in different ways. Start with the content and the destination’s accepted formats, then compare exports. JPEG is a practical choice for ordinary photographs when transparency is unnecessary. PNG is useful when alpha or crisp graphic boundaries matter. Static WebP is another supported option when the destination accepts it. A fashionable extension is not a substitute for checking the real file.

The format is a real encoding choice here, not a filename change. A JPEG output is encoded as JPEG, and the result reports its actual MIME type and bytes. Renaming photo.png to photo.jpg in a file manager does not convert the contents. Keep an original and compare results at the same display scale before deciding that one format is better for this particular image.

Why local tools need honest resource limits

The compressed input is only part of the memory cost. A decoded 4000 × 3000 RGBA image represents 48000000 bytes before working buffers and the output are considered. A batch of large originals can therefore be demanding even when each file looks small on disk. Sequential processing reduces simultaneous work, but it cannot make a device’s memory unlimited.

Admission limits are 25 MiB per file, 24 megapixels, 8192 px per side, 50 files and 250 MiB of queued input. A job below those headline limits can still be rejected if its intermediate image buffers exceed the working budget. On a constrained device, use fewer files or a smaller source and keep the original elsewhere. Cancel and clear are useful controls, not signs that a larger job is guaranteed to succeed on retry.

The download is the final test

A preview is helpful, but the saved output is what the receiving app will use. Check its actual dimensions, MIME type and exact bytes. Open the file in an image viewer, inspect the important details at a sensible scale, and confirm that transparency or the chosen background behaves as expected. If you created a ZIP, open it and compare its successful entries with the expected count.

When a result fails, change the constraint that is actually responsible. Wrong shape calls for a geometry decision; unreadable text calls for more detail or less aggressive encoding; excessive bytes call for a permitted compression or dimension change. Keep each candidate separate until you choose the final one. The original remains your reliable starting point for every new export.

1. Check the real width and height, not only the requested box.
2. Compare exact bytes with the destination’s ceiling.
3. Inspect faces, lettering, product edges and transparent boundaries.
4. Save the chosen output and keep the original separately.