Numbering: Add Sequential Numbers to File Names
Batchio's Numbering Sequence rule adds incrementing numbers to your filenames with full control over the starting value, step size, zero padding width, and placement. Whether you need a simple counter appended to each file or a custom format like Photo_001, the live preview shows the result for every file before you rename.
How do you add sequential numbers to file names?
Sequential numbering is essential for organizing files that need a clear, sortable order. Photographers number shots from a session, editors number chapters or scenes, and archivists number scanned pages. Batchio lets you pick the position for the number, configure the starting value and increment, and preview the entire sequence in the live preview before applying. The numbers follow the current sort order of the file list, so you can drag files into the right sequence first and then number them.
You can place the number as a prefix (before the filename), a suffix (before the extension), or as a full replacement that discards the original name entirely. The replacement option is useful when you want clean, number only filenames like 001.jpg, 002.jpg, and so on. Combined with an Add Text prefix, you can build names like Vacation_001.jpg in a single workflow.
What is zero padding and how does it work?
Without zero padding, file managers sort numbers lexicographically, which means 1 comes before 10 but after 09. This creates a chaotic sort order in folders with more than nine files. Zero padding solves this problem by guaranteeing that every number has the same character length. A three digit pad means files sort as 001, 002, ... 010, ... 100, keeping everything in the correct numerical order regardless of the file manager used.
Batchio lets you set any padding width from 1 to 10 digits. Choose a width that accommodates the largest number in your batch. For a folder of 500 images, a width of 3 is sufficient. For a library of 10,000 scanned documents, use 5. The live preview shows the padded numbers for every file instantly, so you can verify the alignment before committing.
Can you set a custom start number and step increment?
Custom start numbers are useful when you are adding files to an existing numbered series. If your last batch ended at 250, set the start to 251 and the new files continue the sequence seamlessly. The step increment lets you leave gaps between numbers for future insertions. Setting a step of 10 means you can later slot new files into positions 101, 102, and so on without renumbering the entire collection.
These settings apply globally to the entire batch. Every file in the list receives the next number in the sequence based on the start and step values you configure. The live preview displays the exact number each file will receive, so you can confirm the range before applying. If the numbers do not look right, adjust the start or step and the preview updates immediately.
How do custom number formats work in Batchio?
Photo_### produces Photo_001, Photo_002, and so on. The number of hashes determines the zero padding width.Custom formats give you the flexibility to embed the sequential number inside a larger naming template. The hash characters act as a placeholder that Batchio fills with the current number, padded to the width of the placeholder. A format like Scan_####_final produces Scan_0001_final, Scan_0002_final, and so on. This eliminates the need for a separate Add Text rule to wrap the number in surrounding text.
You can combine the custom format with a Date Insertion rule to build names like 2026-03-26_Photo_001.jpg. The Numbering Sequence rule handles the counter, and the Date Insertion rule supplies the timestamp. Our guide to sequential numbering covers zero padding, custom formats, and multi rule workflows in detail.
Number Your Files the Right Way
Download Batchio free on the Mac App Store. All 9 rule types included. Pro upgrade $4.99.
Coming Soon to the Mac App Store
Marcel Iseli is an indie app developer and the creator of Batchio. He builds native macOS utilities focused on productivity and file management, with a focus on lightweight, subscription-free tools.