Processing a few hundred photos one at a time, opening each in an editor, applying a setting, and exporting, isn't just slow, it's also where inconsistency creeps in: a slightly different quality setting here, a wrong aspect ratio there. Batch processing solves both problems by applying one defined operation uniformly, but it works best with a specific workflow rather than throwing every file at a tool and hoping for the best.
Always keep an untouched original set
The single most important batch-processing rule is to never overwrite your originals. Compression and resizing are typically one-directional, you can't recover detail that's been discarded, so if a batch job used the wrong settings, having the untouched originals means you can simply redo it correctly rather than losing the photos permanently. Keep the source folder separate from the processed output folder as standard practice.
Match the tool to the actual goal
If the goal is smaller file sizes for storage or web upload, Batch Image Compressor applies one compression setting across every photo in the set. If the goal is uniform dimensions, say, preparing product photos that all need to be exactly 1200x1200, Batch Resize Images handles that without manually resizing each one. If you're standardizing file formats across a mixed folder, for instance converting a batch of HEIC and PNG files to a consistent JPG, Batch Image Converter does the conversion in one pass. Doing rotation corrections across many files (common with scanned documents or camera photos that were shot sideways) is handled well by Batch Rotate Image.
Test on a small sample before running the full batch
Before applying a setting to hundreds of files, run it on 5-10 representative photos first and check the results, particularly if the set includes a mix of image types (some very detailed, some simple), since a compression or resize setting that looks fine on one photo can behave differently on another. Once the settings are confirmed on the sample, running the full batch with confidence saves far more time than discovering a problem after processing everything and having to redo the whole set.