Tetris Fumen Explained: Read, Make and Share Diagrams

Our perfect clear guide quotes 84.64% for the Perfect Clear Opener when you keep the I on hold. Hard Drop's PCO article gives the same figure as 711 out of 840, calls it the chance to succeed "in theory", and lists solution-finder among its external links as a tool partly used to write the article. That 840 is not a count of games anyone played. It is a count of piece orders, the kind of number a program like solution-finder produces by reading a board diagram, and the diagram format those tools read is fumen: a string that starts v115@ and packs a whole multi-page Tetris board into a link.

This is how to read one, which editor to open it in, what its switches do, and how a percentage gets out of it.

A Tetris diagram editor from 2005

Fumen is a browser-based Tetris field editor by Mihys, whom tetris.wiki identifies as the developer of DTET. The original lives at fumen.zui.jp under its Japanese title, 連続テト譜エディタ. You paint a board, place one piece per page, add captions, and the editor writes the whole sequence out as text you can paste anywhere a link fits.

Mihys keeps the changelog inside the page itself, as a comment in the HTML source, and it dates each part of the format:

That last entry is dated 25 September 2026, and the page now carries the policy it describes. Hard Drop's wiki article on fumen still names 1.15e, from November 2021, as the latest version.

The version you will actually see is in the link. v115 is the data format from Ver 1.15: a field 10 wide and 23 tall, plus one garbage row under the floor. v110 is the older 21-row format. knewjade's tetris-fumen library decodes both and writes only v115, and solution-finder, covered below, accepts only v115.

Three editors, one format

Hard Drop's copy is a fork, and its changelog shows it. A note signed by zyphdoz explains that the "1.15f" add-ons were taken from fumen.sixwi.de and made by swng, and that the page title was deliberately left at 1.15e so the number would not collide with any future official 1.15f from Mihys. One entry in that fork's changelog matters if you share links. Ver 1.15f3 (20 December 2025) fixed a security issue that allowed remote script execution on the Hard Drop wiki, and added support for a #? link form that the changelog says allows much longer character limits; the editor now outputs its links that way. Old ?v115@ links still open, because the editor's code reads both forms.

The Output Diagram code button is the bridge to the Hard Drop wiki. It converts the current page into the wiki's own {{pfstart}} and {{pfrow}} diagram template, the same template articles such as Hard Drop's PCO page use to draw their boards. The add-on's source opens with a message dated 13 January 2011 from Chopin of harddrop.com, asking Mihys whether fumen could convert into diagram code for the wiki.

Reading the string

Take the seven-page example from the README of knewjade's tetris-fumen library:

v115@vhGRQYHAvItJEJmhCAUGJKJJvMJTNJGBJFKYPAUEzP?EJG98AQmqhECDdCA

• v is the mode. When the original editor outputs data it builds three links: v to edit, m for the view-only player, and D for a list of every page. The last two appear as the VIEW and LIST links.
• 115 is the format version.
• @ separates the header from the data.
• The rest is the diagram, written in a 64-character alphabet: A to Z, a to z, 0 to 9, plus + and /.
• The ? is padding, not data. The encoder inserts one after every 47th character, and knewjade's decoder deletes every ? and any whitespace before it reads a page, so a fumen pasted across two lines still decodes.

Per the tetris-fumen decoder, each page holds three things:

• The field, stored as the cells that changed since the previous page. A page whose field did not change costs a repeat counter instead of a board.
• One piece and its flags in three characters: the piece, its rotation (spawn, right, reverse or left), its x and y, and the Lock, Rise, Mirror and colour flags.
• An optional comment, which later pages inherit until a new one replaces it.

That is how the example fits seven pages, seven pieces and two captions into 58 characters of data. The pages chain: once a page's piece locks, the decoder clears any full lines, applies Rise, then Mirror, and the result is the field the next page starts from. Mihys's original editor caps a diagram at 2,000 pages.

Two strings can hold one diagram. Load that README string into Hard Drop's editor and it outputs v115@vhGRQYHAvItJEJmhCAUmBKpBvsBTtBGhBFqQPAUEzP?EJG98AQmqhECDdCA. Decode both and the seven pages match cell for cell. The only difference is the colour flag, which the README string sets on all seven pages and Hard Drop's output sets on the first page only. Compare boards, not text.

Lock, Rise, Mirror, Guideline and Quiz

The colour switch is why two screenshots of the same setup can look unrelated. Mihys added a piece colour pattern in Ver 0.95a (18 March 2006) and made it the default in Ver 1.10. The colour table in the page source puts Guideline mode on cyan I, orange L, yellow O, red Z, magenta T, blue J and green S, the same assignments our Guideline explainer lists as the official colours. Untick it and I turns red, T cyan, S magenta and Z green. The original editor reads the flag from the first page only, so it sets the palette for the whole diagram.

Quiz mode turns a diagram into a drill. solution-finder's own pattern docs give #Q=[](Z)ILJTOS as an example: nothing in hold, Z as the current piece, ILJTOS as the queue. Per the tetris-fumen quiz code, the caption updates itself as pieces lock. Place the current piece and the queue advances. Place the held piece and it records a swap. Place the next piece while hold is empty and the current piece goes into hold.

Reading one on your phone

The desktop editors are dense on a phone screen. knewjade's Fumen for Mobile takes the same data after #?d= in its URL, and adding &lng=ja forces Japanese; otherwise it follows your browser language and falls back to English. Three things to know when you open one:

• The Next column is the pages ahead, not a randomizer. On page 1 of the example it shows Z, L, S, O and J, which are the pieces placed on pages 2 to 6.
• The caption bar is the page comment. Pages 2 to 6 of the example reuse page 1's "Opening"; page 7 carries its own "T-Spin Double".
• Open in Hard Drop hands the same data to harddrop.com/fumen/? when you want the desktop tools.

From diagram to percentage

solution-finder, which ships as sfinder.jar, is knewjade's MIT-licensed command-line tool for searching piece placements. It needs Java 8 or later, 64-bit, and its newest GitHub release is v1.43 from 5 September 2023. Its commands include percent (the chance of a perfect clear from a field), path (every perfect clear route), setup, ren for combos, spin for T-spins, cover for how many piece orders a set of placements works on, and util fig to draw images from a fumen.

It takes the fumen as input. The documented basic call is:

java -jar sfinder.jar percent --tetfu v115@… --patterns *p4

Options can also ride inside the fumen's own comment. 4 --patterns *p4 --hold avoid means clear four lines for the perfect clear, try every order of four different pieces from a bag, and forbid hold.

The pattern sets how many piece orders get counted:

Then the defaults: hold allowed (--hold avoid turns it off), SRS kicks, soft drop allowed (--drop harddrop limits it to hard drops, and 180 needs a kick file that supports 180s), and four lines to clear. The output reads like the documentation's own sample run, success = 99.84% (5032/5040), followed by rates broken down by the first three pieces and up to 100 of the orders that failed.

Now read the PCO numbers again. Hard Drop gives 711/840 with the I held and 514/840 with the I standing in the box, and the text above its rate table says the figures assume hold and a 7-bag randomizer. 840 is 7 × 6 × 5 × 4: every order in which four different pieces of a fresh bag can arrive, the same space as *p4 and I,*p4 above. solution-finder's documentation uses a PCO field with the I already in the box as its own example, with 4 in the comment and *p4 on the command line. The same docs' Grace System fumen carries 4 --patterns T,*p4 in its comment, T on hold, and Hard Drop's Grace System article puts that setup at 88.6%.

So 84.64% is a statement about piece orders under stated rules, not a win rate. When two guides quote different rates for the same shape, compare their hold setting, drop setting and pattern before you compare the shapes. The openers guide quotes perfect clear rates for TKI-3 and MKO branches, and the same questions apply to each of them.

Making your own

• Hard Drop's editor, on desktop. Place Blocks paints cells in the colour you pick, Mino places a piece with the arrow and rotate buttons, Next adds a page, and unticking Lock leaves the piece in mid-air. Output Data writes the string plus the URL, VIEW and LIST links; tick Auto Output to keep them current as you edit.
• Fumen for Mobile, on a phone. The pencil opens edit mode on whatever you loaded.
• tetris-fumen, in code. knewjade's npm package, MIT-licensed, decodes v110 and v115 and encodes v115, with a field model that describes the board as 10 by 23 plus one garbage line.
• solution-finder, to test a claim. Paste the setup, set the pattern and hold rule the claim implies, and see whether the number comes back.

If you are learning a setup from our T-spin guide or the perfect clear guide, building it page by page in an editor is a fast check that you actually know the piece order, and a quiz caption turns it into a drill. The randomizers guide covers why a 7-bag makes those piece orders countable in the first place.

Quick Action Checklist

• Read a fumen link left to right: mode letter (v, m or D), version (115 or the older 110), @, then the pages.
• Ignore the ? marks inside the data; decoders strip them.
• Open links on a phone with Fumen for Mobile, pasting the data after #?d=.
• Expect newer Hard Drop links in the #?v115@ form; older ?v115@ links still load.
• Check the Guideline tick before you trust a screenshot's colours; unticked, the I is red and the T is cyan.
• Untick Lock to show a piece mid-air, use Rise for garbage, and Mirror to publish both sides of a setup in one link.
• Compare two fumens by decoding them, not by comparing strings.
• Before quoting any perfect clear rate, find its pattern, hold rule and drop rule; Hard Drop's PCO figures are out of 840 piece orders with hold allowed.