Deploy modrinth-modpack

Deploy and Host

Deploy a full modded Minecraft server from any Modrinth modpack. Paste a pack URL, project slug, or version URL into the one deploy prompt — the server downloads and installs the entire pack (mods, configs, loader) on first start, then boots into a joinable server with RCON enabled.

Deploy on Railway

About Hosting

• One prompt: MODRINTH_MODPACK — any Modrinth modpack reference: a project page URL (https://modrinth.com/modpack/...), a version page URL (pins that exact version), a project slug (cobblemon-fabric), or a project ID. The pack install runs on first boot: a light pack boots in about 2 to 5 minutes, larger packs take longer.
• Java base: the image pins itzg/minecraft-server:2026.10.1-java21. This covers the pack ecosystem for Minecraft 1.20.5 through 1.21.x (Java 21), which is the vast majority of current Modrinth packs. Packs targeting Minecraft 26.x need Java 25: after deploy, swap the service image to itzg/minecraft-server:2026.10.1-java25 (same digest-pinning pattern) in Settings. Packs are Java-pinned by their mods, so a mismatch crashes at boot with a clear class-version or depends java error in the deploy logs.
• Memory: MEMORY defaults to 4 GB (set MEMORY before first deploy for heavy packs). Measured reference: the Cobblemon 1.21.1 pack idles at about 3.7 GB RSS with a 4 GB heap. Guidance: light SMP or performance packs 4 to 6 GB, mid-size packs 6 to 8 GB, big kitchen-sink packs 12 to 16 GB.
• Cost honesty: Railway bills 24/7 server uptime by the second. At typical rates, 4 GB 24/7 costs roughly 35 to 45 USD per month, 8 GB roughly 70 to 90 USD per month, 16 GB roughly 150 to 180 USD per month — specialist Minecraft hosts are cheaper for always-on heavy packs. Railway wins for intermittent servers (friend groups playing evenings and weekends) where per-second billing and instant deploy/destroy beat a monthly subscription, and for packs that need to live next to your other services.
• Persistence: a volume is mounted at /data — world, mods, configs, and loader all survive redeploys and restarts.
• EULA: the Minecraft EULA is accepted by the image (EULA=TRUE) so the server boots unattended. By hosting a server you accept the Minecraft EULA.
• RCON: enabled on port 25575, internal only. The generated password is in the Variables tab (RCON_PASSWORD, random per deploy). Use it with any RCON client or an MCP RCON control template to send commands (list, say, whitelist, backups) without opening the game.

Why Deploy

• Paste-a-pack simplicity: every other Minecraft template here starts from a bare server or a panel. This one installs the modpack you point it at — the pack choice is the only decision.
• Verified install path: the deploy battery proves the whole chain: pack download and install in the logs, the Done (X.XXXs)! boot line, a live RCON round-trip, a Minecraft status ping through the public join address, and world-plus-mods survival across redeploys.
• Pack updates are a variable edit: change MODRINTH_MODPACK to a newer version URL and restart — the installer cleans up the previous pack's files and installs the new one.
• Ops built in: crash-only restart policy (no fake healthcheck for a non-HTTP game port), per-second billing, volumes, and RCON for scripted control.

Common Use Cases

• Friend-group modded servers: paste the pack your group plays, share the join address from the Variables tab (RAILWAY_TCP_PROXY_DOMAIN:RAILWAY_TCP_PROXY_PORT), stop paying when the group moves on.
• Testing a modpack server-side before inviting anyone: deploy the pack, check the logs, connect once, destroy the project — you pay only for the minutes used.
• Version-pinned community servers: use a version page URL so the pack never drifts until you choose to bump it.
• Automated servers: RCON (password in Variables) drives commands, announcements, and backup hooks from scripts or an MCP control template.

Dependencies for

Deployment Dependencies

• A Modrinth modpack reference for MODRINTH_MODPACK — browse modrinth.com/modpacks. Pick packs marked playable server-side; most popular packs (Cobblemon, Better MC, Prominence, and similar) are. The install fails fast with a clear log line if a pack is client-only or references unavailable files.
• No other services needed — single service, no database. The world lives on the attached volume.
• Clients need the same pack: players install the matching pack from Modrinth (the Modrinth app handles this) and join via the TCP proxy address shown in the Variables tab.
• Java pairing: the pinned image is Java 21 for Minecraft 1.20.5 to 1.21.x packs. For Minecraft 26.x packs, swap the image to the java25 variant after deploy (see About Hosting).