Filter words are the verbs that sit between your point-of-view character and the thing they're experiencing — words like saw, heard, felt, noticed, realized, watched, wondered, thought. They name the act of perceiving instead of just showing the thing perceived. "She saw the door swing open" filters the moment through her perception. "The door swung open" puts the reader in the room.

They're not grammatical errors. They're not even always wrong. But in fiction written in close third or first person, they quietly add distance to almost every line they touch, and most first drafts are full of them. Learning to see them is one of the highest-leverage self-editing skills you can build, because once you can spot a filter word, the fix is usually to delete it and tighten what's left.

What exactly is a filter word?

A filter word is any verb of perception or cognition that reports your character noticing, sensing, or thinking something, rather than rendering that thing directly. The structure is almost always [character] + [perception verb] + [the actual content]:

  1. She heard footsteps in the hall.
  2. He felt the cold creep up his arms.
  3. I noticed that the lights were off.
  4. They watched the train pull away.

Strip the filter and the content stands on its own:

  1. Footsteps echoed in the hall.
  2. Cold crept up his arms.
  3. The lights were off.
  4. The train pulled away.

The second version of each is shorter, more immediate, and — this is the part that matters — already implies the character's perception. If we're in her head, we already know she's the one hearing the footsteps. Saying so is redundant.

The usual suspects

These are the verbs that filter most often. Search your manuscript for them and you'll find the bulk of the problem:

  1. Sight: saw, watched, looked, noticed, observed, spotted, glimpsed
  2. Sound: heard, listened
  3. Touch/sensation: felt
  4. Thought: thought, wondered, realized, knew, decided, considered, remembered
  5. Smell/taste: smelled, tasted

"Felt" and "saw" are the two that show up most. "Realized" is the sneakiest, because writers reach for it at exactly the moments they most want to land — the small revelations — and it deflates every one of them. "She realized the house was empty" is a line about realizing. "The house was empty" is the empty house.

Why filter words weaken fiction

Close POV works by collapsing the gap between reader and character. When it's working, the reader isn't watching the character experience the scene — the reader is the character, more or less. Filter words reintroduce the gap. Each one is a tiny reminder that you're being told about an experience secondhand.

There's also a rhythm cost. Filter constructions are wordier by design, and they bury the interesting noun behind a flat verb. The vivid image in "she saw the field catch fire in the last of the sun" is field, fire, sun — and all three arrive late, after the throat-clearing of "she saw." Cut the filter and the image leads: "the field caught fire in the last of the sun."

Stack a few hundred of these across a manuscript and the prose reads as slightly muffled without the reader ever being able to say why. That's the real danger. Filter words rarely produce a sentence bad enough to flag on its own. They degrade the whole thing by a few percent, everywhere.

When filter words are the right call

This is where most advice on the topic falls down, so it's worth being precise: you should not delete every filter word, and a manuscript scrubbed clean of them can read as oddly flat and overwrought.

Keep the filter when:

  1. The act of perceiving is the actual event. "She listened" is a beat of action — she's straining to hear something — not a filter for what she heard. "He watched her go" is about the watching: the lingering, the not-following. Don't cut those; they're doing real work.
  2. You're deliberately pulling back. Sometimes you want distance — a numb character, a clinical narrator, a scene viewed through shock or dissociation. Filtering can render that remove on purpose.
  3. You're disambiguating POV. In a scene with two characters present, "Maria noticed the gun first" tells us whose head we're in and that she registered it before the other character did. Cutting the filter could blur whose perception we're following.
  4. The unfiltered version creates a false claim. "The roof was about to collapse" states it as fact. "She was sure the roof was about to collapse" keeps it as her (possibly wrong) judgment. The filter carries meaning here.

The test is simple: does the perception verb add information, or is it just announcing that the POV character perceived something we'd assume they perceived anyway? If it's the latter, cut it.

How to run a filter-word pass

Treat it as its own editing pass, late in revision, after the structural work is done. You're not rewriting; you're tightening.

  1. Search for the suspects one at a time. Use your editor's find function and go through felt, saw, heard, noticed, realized, watched, and thought individually. Doing them one verb at a time keeps you from glazing over.
  2. For each hit, try deleting the filter and reading the result. Most of the time the sentence improves instantly. "I felt my heart pound" becomes "My heart pounded."
  3. Tighten what's left. Cutting the filter often exposes a clumsy clause underneath. "She saw that the lock had been broken" → "The lock had been broken." Drop the orphaned that while you're there.
  4. Keep the ones that earn it. If deleting the filter loses information or flattens an intentional bit of distance, leave it. Judgment beats rules.
  5. Don't trust your eye alone. Filter words hide in plain sight precisely because they're grammatically invisible. A read-aloud pass or a prose-checking tool that flags them by category catches the ones you've stopped seeing.

If you write in Pendrilo, the prose checker flags filter words as their own category during a self-edit pass, so you can walk them one at a time instead of eyeballing the whole manuscript — but a plain find-and-replace through the list above gets you most of the way there in any editor.

Filter words vs. weasel words — not the same problem

It's easy to lump these together, but they're different failures. Weasel words and crutch phrases (just, really, very, somewhat, a bit) are hedges and intensifiers that water down a sentence's force. Filter words are perception verbs that add narrative distance. A sentence can have one, both, or neither. You'll often run both passes back to back late in revision, but you're hunting two different animals: weasel words dilute, filter words distance.

Get the filter words out and the difference is immediate. The reader stops being told what your character notices and starts noticing it themselves. That's the whole game.