Bulk Rename Images

The four controls, and what they do in order

A bulk renamer combines a small number of predictable operations, and understanding the order they apply in explains nearly every naming problem. A prefix goes at the front, a suffix at the end, sequential numbering sits between them, and a find and replace runs across the result. The practical point is that numbering applied to a folder where every file already has a number in its name will produce results like photo-2-1.jpg, which is why clearing existing numbers first usually produces a cleaner set.

NoteNumbering on names that already contain numbers produces doubled numbers. Replace the existing digits first.

Why sequential numbering matters for a set

A folder of photographs from an event arrives with names from a camera, a download, or a messaging app, and none of them are in order. A gallery, a client handover, or a slide deck needs them in a sequence that matches the running order, and manual renaming of a hundred files is not realistic. Numbering solves it in one pass, and because the numbers are padded to the same width, they sort correctly in a file browser. Without padding, 10 comes before 2 in an alphabetical sort, which is the failure that catches people.

• Camera names are not in shooting order. A folder rarely is either.
• Numbering puts a set in running order in one pass.
• Pad the numbers to equal width so 2 sorts before 10.
• Start the numbering where the previous set ended if continuing a series.
• Check the preview before committing, especially with a prefix in use.

NoteWithout padded numbers, a file browser sorts 10 before 2 and the order is wrong.

Extensions, and the mistake that breaks a set

Renaming tools differ in whether they preserve the file extension, and a name that becomes photo.jpg.jpg is the usual symptom of a tool that treats the extension as part of the name. Every image also keeps its format, so a folder with a mixture of JPG, PNG, and HEIC will still contain a mixture after renaming, which matters if the destination is a system that accepts only one. Renaming does not convert anything, and it does not change the pixels, the dimensions, or the file size. A renamed file is byte for byte the same file under a different name.

• Check that the extension is preserved, not appended twice.
• Renaming does not convert formats. A HEIC stays a HEIC.
• A renamed file is identical, only the name differs.
• Convert formats separately if the destination requires one type.

NoteRenaming changes the name only. It does not convert, compress, or resize.

Getting the order right before you commit

The most valuable habit is to read the preview rather than trust the settings. Renaming is not destructive to the image, so a wrong result is cheap to fix, but it is not free: the files have to be saved again, and a set that was numbered wrong may have overwritten names that were already meaningful. Reading a preview of twenty lines takes a few seconds and catches a duplicated prefix, a doubled extension, or a number sequence that starts in the wrong place. It is also the only way to spot a find and replace that matched something unintended.

• Read the preview. A wrong rename is cheap to fix but not free.
• Look for a duplicated prefix or a doubled extension.
• Check that the numbering starts where you intended.
• Confirm the find and replace did not match something unintended.
• Keep the original names in a note if the set matters.

NoteA twenty line preview read takes seconds and catches nearly every naming mistake.