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Canister resource limits

Beginner
Developing canisters

The Internet Computer uses WebAssembly as the platform for executing messages of canisters. Since WebAssembly is Turing-complete, it can express different kinds of computations, including non-terminating computations. The Internet Computer protects against non-terminating computations by limiting the number of WebAssembly instructions and other resources per message execution. The limits depend on the message type as shown in the following table.

Resource constraints and limits​

Message resource limits                                                              Constraint  
Message queue limit, messages per canister                                          500        
Maximum ingress message payload                                                      2MiB        
Maximum cross-net inter-canister message payload                                    2MiB        
Maximum same-subnet inter-canister request payload (may be deprecated at some point)10MiB        
Maximum response size (replicated execution)                                        2MiB        
Maximum response size (non-replicated execution, i.e., in query calls)                3MiB        
Instruction resource limits                                                          Constraint  
Instruction limit, instructions per update call/heartbeat/timer                      40 Billion  
Instruction limit, instructions per query call                                      5 Billion  
Instruction limit, instructions per canister install/upgrade                        300 Billion
Instruction limit, instructions per inspect_message                                  200 Million
Instruction limit, instructions per round per execution thread                      7 Billion  
Subnet limits                                                                        Constraint  
Subnet capacity (total memory available per subnet)                                  1TiB        
Maximum number of snapshots per canister                                              1          
Memory resource limits                                                              Constraint  
Wasm heap memory, per canister                                                      4GiB        
Wasm stable memory, per canister                                                    500GiB      
Wasm stable memory, data access per replicated message                              2GiB        
Wasm stable memory, data written per replicated message                              2GiB        
Wasm stable memory, data access per upgrade message                                  8GiB        
Wasm stable memory, data written per upgrade message                                8GiB        
Wasm stable memory, data access per (replicated) query                              1GiB        
Wasm stable memory, data written per (replicated) query                              1GiB        
Wasm module limits                                                                  Constraint  
Wasm total size, per canister                                                        100MiB      
Wasm code section, per canister                                                      10MiB      
Wasm custom sections, per subnet                                                    2GiB        
Wasm custom sections, per canister                                                  1MiB        
Wasm custom sections, sections per canister                                          16          
Query call resource limits                                                          Constraint  
Query calls execution threads, per replica node                                      4          
Query calls execution threads, per canister                                          2          
Update call resource limits                                                          Constraint  
Update calls execution threads, per subnet                                          4          
Update calls execution threads, per canister                                        1          

Performance limits​

The block rate varies from 0.75 blocks per second to 1.5 blocks per second depending on the subnet and the number of nodes in the subnet.

Up to 1000 messages can be included in a block. Since ICP decouples message reception from message execution, the messages included in a block are not guaranteed to be executed in the same block. Messages for different canisters may be executed in parallel on multiple threads. ICP currently has 4 execution threads, and each thread can execute up to 1000 messages. Another limiting factor in execution throughput is the number of executed Wasm instructions. ICP currently targets 2B instructions per block.

Additional notes​

The expiration time of an ingress message is specified by the agent making the request and can be up to 5 minutes.

The Internet Computer Protocol may reject WebAssembly modules for reasons such as:

  • They declare more than 50_000 functions.
  • They declare more than 1_000 globals.
  • They declare a function with more than 1_000_000 Wasm instructions.
  • They declare more than 16 exported custom sections (the custom section names with the prefix icp:).
  • The number of all exported functions called canister_update <name> or canister_query <name> exceeds 1_000.
  • The sum of <name> lengths in all exported functions called canister_update <name> or canister_query <name> exceeds 20_000.
  • The total size of the exported custom sections exceeds 1MiB.

More information regarding these restrictions can be found in the Internet Computer interface specification.