A1SI-TERM comparison
A1SI-TERM vs PuTTY & Tera Term
PuTTY and Tera Term are excellent terminals. They are free, open source, lightweight, and have earned decades of trust on millions of desks — for a quick SSH session or a serial console, they are hard to beat, and we use them ourselves.
A1SI-TERM is built for a different job: the regulated and industrial environments where one operator needs SSH, Serial, Telnet, Raw TCP/UDP, SFTP, and Modbus RTU in one application, with an audit transcript and an e-signature on every regulated session. This page lays out the differences fairly so you can pick the right tool.
Feature comparison
| Feature | A1SI-TERM | PuTTY | Tera Term |
|---|---|---|---|
| License & cost | Commercial (early access) | Free, open source (MIT) | Free, open source (BSD) |
| SSH | YesYes | YesYes | YesYes |
| Telnet | YesYes | YesYes | YesYes |
| Serial (RS-232 / 422 / 485) | YesYesFull option set, RTS/DTR/BREAK, replug-aware reconnect | YesYesRS-232 serial | YesYesSerial |
| Raw TCP / UDP | YesYesRaw TCP byte-stream and UDP datagram | YesYesRaw TCP | NoNo |
| SFTP file transfer | YesYesDual-pane browser, resume, SHA-256 verify, directory diff | NoNoCompanion PSCP/PSFTP command-line tools | NoNoSCP only |
| Modbus RTU industrial decode | YesYesLive frame decode with CRC + register-map overlays | NoNo | NoNo |
| 21 CFR Part 11-aligned audit transcripts | YesYesHash-chained, Ed25519-signed, deterministic replay (aligned, not certified) | NoNo | NoNoPlain session logging only |
| E-signature ceremony (§ 11.200) | YesYesIdentity, meaning, and justification captured before action | NoNo | NoNo |
| Paste sanitizer (escape-injection defense) | YesYesStrips OSC 52, DCS passthrough, DA/DSR poison before paste | NoNo | NoNo |
| Command-policy engine | YesYesDeclarative warn / confirm / block rules on outgoing commands | NoNo | NoNo |
| Credential storage | OS keychain + Argon2id-wrapped AES-256-GCM vault | Pageant agent; keys on disk | ssh-agent; keys on disk |
| Saved hosts, groups & ssh_config import | YesYesHost tree, groups, recursive Include / ProxyJump / Match import | YesYesSaved sessions | YesYesSaved sessions, macro (TTL) scripting |
| Tabbed sessions in one window | YesYesTabs + broadcast typing across tabs | NoNoOne window per session | NoNoOne window per session |
| Platforms | Windows, macOS, Linux | Windows (unofficial *nix ports) | Windows |
PuTTY and Tera Term are independent open-source projects and are not affiliated with or endorsed by A1 Systems Integrators. Capability entries reflect each tool’s core, out-of-the-box behavior; both are extensible and actively maintained.
When to choose which
Reach for PuTTY
When you want a free, tiny, battle-tested SSH/Telnet/serial client on Windows with no install footprint, and you do not need file transfer, tabs, or audit trails in the same window. PuTTY is the dependable default for ad-hoc administration.
Reach for Tera Term
When you are on Windows and want a free terminal with strong serial support and TTL macro scripting for repeatable device interactions. Tera Term is a long-standing favorite for embedded and networking bench work.
Reach for A1SI-TERM
When you work in a regulated or industrial setting and need one cross-platform application that unifies every transport, decodes Modbus RTU live, sanitizes pastes, enforces command policy, and records 21 CFR Part 11-aligned, e-signed audit transcripts — capabilities PuTTY and Tera Term do not target.
Our honest take
Most teams do not need an audit-ready terminal, and for them PuTTY or Tera Term is the right answer — free tools that do their one job well. A1SI-TERM earns its place only where the audit trail, the e-signature ceremony, the policy engine, and the industrial-protocol decode are genuinely required, and where consolidating five tools into one native window is worth a commercial license.
The 21 CFR Part 11 capabilities are aligned with the standard — A1SI-TERM produces the hash-chained transcripts and e-signature artifacts regulated workflows depend on, but it is not itself a certified or validated system. See the Trust Center for the full certified-vs-aligned breakdown.
See the full A1SI-TERM picture
Walk through every transport, the regulated-mode workflow, and the industrial-protocol tooling on the product page — then request early access.
Explore A1SI-TERM