What's the maximum number of signers for a given account?

Question

Submitted externally:

Can I specify 1000 people can sign on my addr Or is there a limit in terms of the maximum number of signers?

Answer 1

As of the time of this writing, it's 20. This is specified in the XDR for AccountEntry for the size of the signers collection:

struct AccountEntry
{
    AccountID accountID;      // master public key for this account
    int64 balance;            // in stroops
    SequenceNumber seqNum;    // last sequence number used for this account
    uint32 numSubEntries;     // number of sub-entries this account has
                              // drives the reserve
    AccountID* inflationDest; // Account to vote for during inflation
    uint32 flags;             // see AccountFlags

    string32 homeDomain; // can be used for reverse federation and memo lookup

    // fields used for signatures
    // thresholds stores unsigned bytes: [weight of master|low|medium|high]
    Thresholds thresholds;

    Signer signers<20>; // possible signers for this account

In particular:

Signer signers<20>; // possible signers for this account

This is also specified in the docs under the Set Options operation with regard to the SET_OPTIONS_TOO_MANY_SIGNERS error:

|SET_OPTIONS_TOO_MANY_SIGNERS| -2| 20 is the maximum number of signers an account can have, and adding another signer would exceed that.|