Independent dojos
One sensei, an assistant or two, and a steady group of judoka. C3NTR puts your throws, ne-waza and kata in one place.
For martial arts schools
A knowledge home for your judo dojo.
Throws, ne-waza, the syllabus and the principles of Kano.
→ See a quick tour
Free for up to 30 students
No credit card
UK GDPR · EU (London)
Works offline
Your dojo's curriculum deserves a home
Throw mechanics get taught three ways depending on which sensei is on the mat. Japanese terms get explained again each grading. IJF rule updates miss half the dojo. C3NTR is a quiet place to write it all down once.
Who this is for
Schools with multiple instructors
Several sensei teaching across the week. C3NTR holds the shared standard so every randori draws from the same library.
Competition clubs
Content locked by grade keeps newer judoka safe on basics while shiai-focused players see the deeper game.
Built for teachers, not for IT
Your sensei opens the app, taps Edit, and writes the next throw breakdown in plain prose. The next class, the brown belts read it before kuzushi practice.
Write directly in the app
Like a notepad. New articles are drafts until you publish, so nothing goes live by mistake.
Mobile-first authoring
Edit on the phone between classes or on the way home. The same library, the same edit screen.
A working library in under an hour
Import the starter template in a few taps. Edit anything that doesn't fit. Publish when ready.
Kyu and dan grades
Content locked by grade, in your dojo's kyu and dan
Tag any article with a minimum kyu or dan. New students see ukemi and the first throws. Senior students see ne-waza and competition tactics. Sensei sees everything.
A glossary in Japanese and English
Judo carries the language of the Kodokan. C3NTR's glossary holds the terms in one place: the romaji, your dojo's translation, and the article each term appears in.
- Judo
- Japanese: *judo* (柔道), "the gentle way". The modern martial art founded by Jigoro Kano at the Kodokan in 1882, descended from older Japanese jujutsu schools.
- Kodokan
- The school in Tokyo founded by Jigoro Kano in 1882 as the original home of judo. The name means "school for studying the way".
- Tatami
- The padded mats used in a judo dojo..
- Judogi
- The judo uniform, a heavy cotton jacket, drawstring trousers, and a belt (*obi*). Distinct from the lighter karategi or jiu-jitsu gi.
- Ukemi
- The art of falling safely, literally "receiving body". The most important skill in judo, because it's what allows safe practice of throws.
- Kumikata
- The standard grip in judo, typically right hand on the partner's lapel and left hand on the partner's sleeve. The basis of nearly every throw.
Gradings, shiai, randori-only nights
C3NTR isn't only the library. Schedule the gradings students are working toward, post when a shiai is coming up, and let judoka see what's happening at the dojo this month. Announcements land on their Today tab and events sit on the calendar.
Start from our Judo template
A working starter with 14 articles, 2 short videos, a 11-terms glossary across 5 tags (Getting Started, Foundations, Practice, Progression, Resources). Import in a few taps, then edit anything that doesn't fit your school. Every article, term and tag is yours from the moment you import.
See the Judo template Template source:assets/templates/martial_arts/judo.c3t.md
Inside the app
A look at how the library, articles and grade controls feel in your students' hands.
Plays well with what you already have
Bring your existing kata notes and Japanese terminology in with smart Word document import or paste Markdown directly from your dojo's archive.
Word documents
Smart import reads headings and turns them into draft articles. You review before anything publishes.
Markdown from any editor
Notion exports, Obsidian notes, Bear, plain .md files. Paste or import.
C3NTR templates
Open .c3t.md format. Schools can share templates with each other without us in the middle.
UK GDPR · DPA 2018
UK GDPR compliant. Hosted in the EU (London).
C3NTR is built around UK data protection law from the ground up. Your school's data sits in the EU on Google Cloud London, the same region we manage from.
UK GDPR + Data Protection Act 2018
Built around UK GDPR Article 6 lawful bases. Subject access requests answered within one calendar month.
Hosted in the EU (London)
Your school's data sits on Google Cloud in the europe-west2 (London) region. No transfer outside the UK or EEA for core operation.
Encrypted in transit
All data is TLS encrypted. Access restricted to personnel with a clear business need.
Account deletion on request
Permanent deletion of personal data and content via in-app or written request.
What C3NTR is, and what it isn't
A library your school owns
Another booking or billing system
Built for how schools actually teach
A generic course builder
Calm, focused reading for students
A feed competing for attention
Start free. Move up when you outgrow it.
Seed
Free forever
Up to 30 students
All core features. No credit card.
Start freeSchool
£39/mo
£32/mo billed annually
Up to 150 students
Push notifications. 1 GB media storage.
Choose SchoolAcademy
£69/mo
£57/mo billed annually
Unlimited students
Multi-instructor publishing. Engagement analytics. 5 GB media storage.
Choose AcademyStudent? Show this to your sensei.
If you train judo and you'd love a quiet library between training, share this page with your sensei. Most dojos start on the free Seed plan in under five minutes.
Common questions
Can students only see their grade's material?
Yes. Tag any article with a minimum kyu or dan. New students see ukemi and the first throws. Sensei sees everything.
Does it cover Kano's principles and IJF rules?
Yes. The starter includes articles on jita-kyoei and seiryoku zenyo, and notes on the current IJF rule set with space for your dojo's competition focus.
Can my dojo customise the judo template?
Yes. Every article, throw and term is editable. Add your kata list, your grading syllabus and your dojo's standards.
How long does it take to set up?
Most schools have a working library in under an hour. Import the starter template in a few taps, then edit anything that doesn't fit. Starting blank takes a little longer. Allow an hour or two to write your first ten articles. Students can use the app the day you publish.
Do I have to stop using my booking system?
No. C3NTR is a knowledge library for your curriculum, terminology and progressions. Booking, billing and scheduling stay with the tools you already use.
Is there a free plan?
Yes. Seed is free forever for up to 30 students, with no credit card required. Move up to School (£39/mo) or Academy (£69/mo) when you outgrow it.
Teach a different style? Tell us.
Whether it's a specific judo lineage we don't list, or another discipline entirely, drop us a line and we'll add a starter template. In the meantime, the app already works for any structured curriculum, your library starts blank in a few minutes.
Ready to give your judo students a knowledge home?
Free for the first 30 students. No credit card. A working library in under an hour.
Start free for your school