You can identify where a wormhole leads and what size hulls can fit through it by checking its visual appearance and/or its Show Info window.
Visual appearance ID guide.
Show Info (text-based) ID guide (click to show/hide).
- KS = Known Space, i.e. null, low, and high-security space (NS, LS, HS).
- JS = J-Space, i.e. wormhole space (all wormhole system names start with the letter J).
- JS consists of six main classes of space from C1-C6 and a handful of special ones.
Right-click a wormhole and select Show Info. The top two sentences are irrelevant.
The third sentence (beginning, “This wormhole seems to lead…") narrows down the hole's destination:
- Plain "unknown" space is class 1-3 JS, “dangerous unknown" is C4-5, and “deadly unknown" is C6.
- High/Low/Null Security is that class of KS, "Triglavian" is Pochven and Thera is, you guessed it: Thera.
- If you're currently in KS you can further differentiate C1 from C2/3; if the last sentence says "up to medium ships" will fit, it's a C1.
- To suss C2 from C3 and C4 from C5 you must either yump in, click the system name and check its region, or learn to discern them visually.
- Regions starting with "A-" are C1, B-C2, C-C3, D-C4, E-C5, F-C6. G = Thera, H = C13, K = Drifter.
The fourth sentence indicates a hole's remaining life:
- "This wormhole has not yet begun its natural cycle..." = max life ("fresh").
- "This wormhole is beginning to decay..." = between four hours and max life (also "fresh").
- "This wormhole is reaching the end of its natural lifetime." = 0-4 hours ("EOL" i.e. "end-of-life", “critical" in Tripwire).
The fifth indicates its remaining mass:
- "This wormhole has not yet had its stability reduced..." = over 50% of mass remaining ("stable" or "healthy").
- "This wormhole has had its stability reduced..." = 10-50% of mass remaining (“destab", "shrunk" or “first shrink").
- "This wormhole has had its stability critically disrupted..." = under 10% of mass remaining ("crit").
The last sentence indicates what size class the hole is, i.e. which types of ships will fit through.
- "Only the smallest..." = S: destroyers, ZMPE'd HICs and smaller (these are often called “frigholes", somewhat confusingly).
- "Up to medium..." = M: battlecruisers, industrials, Nestors with no onlined plates and smaller (no other battleships).
- "Larger ships..." = L: all other battleships, Orcas, and smaller (one type of L—Pochven's C729 reverse-static—can also fit Bowheads).
- "Very large..." = VL: either all ships ≤ freighters & jump freighters or all ships ≤ Rorquals/carriers/dreads/FAXes (the latter group includes the former).
WARNING: NOT ALL HOLES OF A PARTICULAR SIZE CLASS WILL ALLOW THE SAME NUMBER OF SHIPS THROUGH.
That is to say: only S holes all have the same total mass limit. M, L and VL vary within their own classes.
For example, D845s—L holes—will pass 5 million tonnes, whereas Unidentified Wormholes—also Ls—only pass 750,000 tonnes.
The jump range of wormholes is 5 km (double that of stargates/Ansiblexes).
To see how much mass a particular hole has, you must identify its type, which is the non-K162 side. Then you can Control + F on this page.
You can also use the above link to check whether a VL is freighter-and-smaller or caps-and-smaller (but don't be dumb with either).
All frigholes are now effectively unrollable.
Unidentified or "Uni" or "Drifter" wormholes have different mechanics to normal holes and are only used for certain purposes.
A quick overview of Drifter hole mechanics.