What DiffLists does
DiffLists is a free, browser-based tool for comparing two lists. Paste or import two sources of text and it calculates the relationship between them entirely in the current browser tab — nothing is uploaded to or stored on a server.
The five result sets
- Only in List 1 — items present in the first list but not the second.
- Only in List 2 — items present in the second list but not the first.
- Intersection — items present in both lists.
- Union — every distinct item across both lists.
- Symmetric difference — everything that appears in exactly one list.
Every comparison also reports raw and unique item counts, duplicates removed, and a match-rate percentage for each list, on the main comparison tool.
The tool list
Alongside the main two-list comparison tool, DiffLists includes 7 single-purpose tools, all free and browser-based:
- Alphabetizer — Sort any list A→Z or Z→A instantly.
- Duplicates Remover — Strip repeated items from a single list.
- CSV Comparer — Compare two CSV exports or columns.
- Intersection & Union Calculator — Compute set operations on two lists.
- Text Diff — See line-by-line changes between two texts.
- Invisible Character Detector — Find hidden characters breaking your data.
- Instagram Follower Checker — See who doesn't follow you back.
See the full list on the tools page.
Privacy facts
- No account, login, or signup for any tool.
- Comparisons run entirely in the visitor’s browser tab using JavaScript.
- List data is not transmitted to or stored on a DiffLists server during normal use of the web tools.
- No third-party tracking pixels embedded in the comparison workflow itself.
The public API (below) is a stateless HTTP endpoint: a request is processed and the response returned without the submitted lists being persisted. See the privacy page for the full policy.
Tech stack
- Built with Next.js (App Router) and React.
- Deployed on Vercel.
- Comparison logic runs client-side in the browser; no backend database stores submitted list data.
Public API
DiffLists has a free, public, unauthenticated API — POST /api/compare — that returns the difference, intersection, union, and symmetric difference of two lists as JSON. No signup or API key is required; requests are rate-limited per IP. Full reference: API documentation.
Embed widget
The comparison tool can be embedded on another site with a single <iframe> snippet — no signup, no API key, no cost. See the embed page for the snippet and options.
Copy-paste description
For directories, listicles, and press mentions:
DiffLists is a free, browser-based tool for comparing two lists. Paste or import two sources and it returns the items only in List 1, only in List 2, the intersection, the union, and the symmetric difference — all calculated locally in the browser, with nothing uploaded to a server. No account or signup is required.
Contact
For press or partnership inquiries, reach out via the details on the about page.