List Deduplicator — Remove Duplicate Items
Remove duplicate items from a list with case-sensitive or case-insensitive matching.
How it works
- 1Paste or type your text in the input field
- 2Click "Process" — processing happens in your browser
- 3Copy the result or download as a text file
What to do next
About List Deduplicator
List Deduplicator runs the text processing job locally inside your browser. Remove duplicate items from a list with case-sensitive or case-insensitive matching. The work happens on your machine, the result is generated on your machine, and the page exposes the controls you need to drive it without burying them in menus.
Reach for List Deduplicator when you need a predictable result on a single file. The page works on the first visit, the controls are visible without a menu, and the output is delivered the moment the engine finishes.
List Deduplicator runs the entire transformation inside your browser. The file is read by JavaScript running in the page, processed in-memory by standard browser APIs, and written back as a download. The browser is the runtime; the page is the interface. You can confirm what the tool does by opening the developer-tools Network tab during a run — the only requests are for the page's own static assets.
Technically, the work is done by standard browser APIs, loaded as part of the page. Inputs are recognised automatically and validated before the engine begins processing. Files up to 0 MB are supported per run; that ceiling keeps browser memory usage stable on a wide range of devices.
The only practical limit is the 0 MB per-file ceiling, which keeps the tool responsive across a wide range of devices. Run the tool ten times in a row, run it ten thousand times — it behaves the same way and produces the same quality of result.
The heaviest users of List Deduplicator tend to be support agents standardising replies, editors comparing manuscript drafts and students formatting essays. Each group brings slightly different expectations to the tool, but the same single-page architecture serves every one of them with the same response time.
The download is delivered as a clearly named file the moment processing completes — no email link, no "your result will be ready in 5 minutes" queue, no expiry timer. The file is generated in your browser and saved by your browser's normal download flow.
List Deduplicator sits in a small group of related tools. Useful neighbours include List Sorter, List Item Counter, Duplicate Sentence Finder, and Compare Two Lists. They are designed to compose: the output of one is a sensible input to the next, so a multi-step task is usually a sequence of single-click operations.
List Deduplicator is built around steady iteration on a small set of options rather than feature creep. Every additional setting attracts a slightly different audience, but a long settings panel makes the common case slower for everyone. The current controls reflect what users of the tool actually use.
Some context on why List Deduplicator exists in this form: modern File APIs, high-performance JavaScript engines, and well-maintained open-source libraries now make it possible to perform text processing work entirely in the browser. List Deduplicator is built on top of that capability, which is why a single page can host the full pipeline.
List Deduplicator produces deterministic output: the same input plus the same options always produces the same result. That predictability matters when the result has to match an upstream specification or be reproducible later.
Tips from users who reach for List Deduplicator regularly: process one input first to confirm the settings produce what you expect before committing to a batch; treat the page as the working surface and avoid leaving large jobs running in a backgrounded tab where the browser may throttle JavaScript; and if a particular file fails, check whether the source is intact by opening it in its native viewer — most "tool errors" are actually input errors.
When something goes wrong, the cause is usually one of three things: a malformed input, a browser that is out of memory, or a corporate proxy that is interfering with the page's static assets. The first two are easy to diagnose; the third typically requires asking your IT team to allow standard browser APIs to load.
List Deduplicator is intentionally narrow in scope so the common case is fast and the result is predictable. If you ever need a variation it does not cover, browse the rest of the catalog — there is a good chance an adjacent tool already exists, and switching between tools is just a matter of opening another tab.
How it works
- 1Open the List Deduplicator workspace above. The interface is a single page, so there is nothing to navigate.
- 2Drop a text file onto the upload area, or click to pick one from your device.
- 3Pick any non-default settings you need. Most users leave the defaults alone for the first run and only revisit if the result needs tuning.
- 4Click to start the job. The engine (standard browser APIs) processes the input in the page; you can watch the progress indicator until it completes.
- 5Save the output when it is ready.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Reformat a JSON blob copied from a log into something readable using List Deduplicator.
- Generate a slug from a long article title.
- Find and replace dozens of variants of a phrase in one pass.
- Diff two drafts of a document side by side.
- Strip messy formatting out of copy pasted from a PDF.
- Translate plain text into Markdown for a static-site post.
- Count the words in a draft to check it fits a brief.
- Convert a column of names into a comma-separated list for a script.
FAQ
Does it preserve order?
Yes — the first occurrence of each item is kept in its original position.
Case-sensitive or insensitive?
Both — choose from the dropdown. Case-insensitive treats "Apple" and "apple" as duplicates.
Does it trim whitespace?
Yes — leading and trailing spaces are trimmed before comparison.
How many items can it handle?
No practical limit — deduplication runs in your browser with O(n) performance.
Can I see which duplicates were removed?
The stats show the count of duplicates removed. The output contains only unique items.
Is my data safe?
Yes — all processing happens locally in your browser. Your text never leaves your device.
Is there a programmatic version of List Deduplicator?
List Deduplicator is a browser-only tool by design and does not expose a hosted API. The reason is the same as the privacy story: there is no Favtoo backend doing the work, so there is no service to call. If you need to script the same transformation, the underlying engine (standard browser APIs) is open-source and can be used directly from your own code.
How accurate is List Deduplicator?
List Deduplicator is built on standard browser APIs, which is the same class of engine used by professional text processing pipelines. For deterministic operations, the output is byte-identical to what an equivalent CLI run would produce; for operations involving a codec or a model, the result is well within the range of what comparable tools generate. If you have a specific reference output you need to match, run a small test job first to confirm the configuration produces what you expect.
Is List Deduplicator licensed for business use?
List Deduplicator can be used for personal and commercial work alike — there is no separate "business" licence to purchase. The output you generate is yours to use however you want, including in client deliverables, internal documents, or commercial products. Favtoo's only ask is fair, individual use; the tool is not designed to be embedded as a backend service or wrapped behind an API for resale.
Does List Deduplicator work in Safari, Firefox, Chrome and Edge?
List Deduplicator works in any modern browser released in the last few years — Chrome, Edge, Firefox, Safari, Brave, Arc and the major Chromium derivatives are all supported. The underlying engine relies on widely-supported web APIs, so there is nothing exotic to install. If you are on a very old browser version and the tool fails to load, updating to the latest release of your preferred browser is the only fix needed.
Can I process multiple files at once with List Deduplicator?
List Deduplicator processes one input at a time by design — it keeps memory usage predictable on lower-end devices and makes results easier to verify. To handle a folder, run the tool once per file; the page stays loaded between runs and remembers your last-used settings, so the second run is essentially instant.
Is the source for List Deduplicator available?
List Deduplicator is a static page running an open-source engine in your browser, so a typical corporate firewall does not get in the way as long as it allows JavaScript to load from Favtoo. For teams that need to host it themselves on an internal network, the underlying engine (standard browser APIs) is open-source and can be packaged into a private build with the same behaviour. Reach out via the Contact page if that is something you are exploring.
Does List Deduplicator ask for any browser permissions?
List Deduplicator only needs the standard web platform — file picker access for the inputs you choose to load, and optionally clipboard access if you copy the result rather than downloading it. There is no microphone, camera, geolocation or background-permission request, because none of those are needed for the work the tool does.
How accessible is the List Deduplicator interface?
List Deduplicator uses native HTML controls wherever possible, which means keyboard navigation, focus rings, and screen-reader labels work the way the platform expects. The drop zone accepts files via the keyboard-accessible file picker as well as drag-and-drop, and result downloads use standard browser download flows. If you spot an accessibility gap, Favtoo treats it as a bug worth fixing.